Method and apparatus for automatic fabrication of three dimensional object

ABSTRACT

A method and apparatus automatically fabricates a three dimensional object from individual layers of fabrication material having a predetermined configuration. Successive layers are stacked in a predetermined sequence and affixed together to form the object. The fabrication material is carried on a substrate to a stacker. At the stacker the layers are stacked together, with each layer being successively affixed to the stack of previously affixed layers, and with the substrate removed from each layer after it is affixed.

RELATED APPLICATION

This application is a divisional application of U.S. patent applicationSer. No. 08/640,549, entitled Method and Apparatus For AutomaticFabrication of Three-Dimensional Objects, filed May 2, 1996, now U.S.Pat. No. 5,879,489 which is a continuation-in-part of U.S. patentapplication Ser. No. 08/157,645, filed Nov. 24, 1993, and entitledMethod and Apparatus For Automatic Fabrication of Three-DimensionalObjects, now U.S. Pat. No. 5,514,232. These related applications areincorporated herein by reference and made a part of this application.

TERMINOLOGY

Conveyed-Adherent: Referring to the method of automated fabricationdescribed herein, in which successive patterns of fabrication materialare formed on a substrate, and then the patterns of fabrication materialare conveyed on the substrate into successive positions, and then thesubstrate is removed from the fabrication material. Conveyed-Adherentautofab may be implemented in either a fully additive or in a hybridfashion. “Conveyed-Adherent” is a trademark of Ennex FabricationTechnologies of Los Angeles.

Carried-Sheet: Referring to a hybrid implementation of Conveyed-Adherentautofab in which the fabrication material is supplied in sheet form, andin which the patterns of fabrication material are determined by cuttingthe shapes of the patterns into successive pieces of the sheet material.“Carried-Sheet” is a trademark of Ennex Fabrication Technologies of LosAngeles.

Fabrication medium: Sheet material moving through a Conveyed-Adherentfabricator, consisting of adjacent substrate and fabrication material.The material moving through a fabricator may be sliced into individualsegments of fabrication medium, or it may be a long, continuousfabrication medium containing the fabrication material for manysuccessive layers.

Positive region: The region of space which is or will be occupied by afabricated object or by material which will form part of a fabricatedobject.

Positive material: Fabrication material which does or will occupy apositive region and therefore does or will compose a fabricated objector part of a fabricated object.

Negative region: The region of space complimentary to a positive region.

Negative material: Fabrication material which does or will occupy anegative region and will therefore be removed.

Weeding: Separation of negative material from positive material in asingle layer of fabrication material in a Carried-Sheet fabricator, socalled because it is the removal of unwanted material.

Lay-down: Establishment of contact of fabrication material with stack.

Peel-off: Incremental removal (peeling) of substrate from fabricationmaterial.

Consequent peel-off: Stacking in which lay-down is completed beforepeel-off begins.

Concurrent peel-off: Stacking in which peel-off is begun while lay-downis still in progress.

Simultaneous peel-off: Concurrent peel-off in which peel-off at eachpoint is approximately simultaneous with lay-down at that point.

Delayed peel-off: Concurrent peel-off in which peel-off at each pointtakes point with some delay after lay-down at that point.

Platen: In a stacker, device that imparts forces on a fabrication mediumto enact lay-down and/or peel-off.

Face of a platen: Portion of the surface of the platen which contacts afabrication medium.

Shape of a platen: Shape of the platen's face.

Holding device or holding system: In a stacker, device or system whichcontrols the motion and tension of the fabrication medium duringlay-down and peel-off.

Holding platen: Combination of a platen to which the fabrication mediumis rigidly held and the portion of the holding system which so holds thefabrication medium.

Flat: Description of a smooth surface at a point through which twodifferent straight lines can be drawn in the surface.

Singly curved (having single curvature): Description of a smooth surfaceat a point through which only one straight line can be drawn in thesurface.

Axis of curvature at a point of a singly curved surface: The onestraight line which can be drawn in the surface through that point.

Doubly curved (having double curvature): Description of a smooth surfaceat a point through which no straight line can be drawn.

Radius of action: In a lay-down or peel-off action being performed byany kind of complicated platen system, the radius of a roller that wouldprovide approximately the same configuration of forces as are actuallybeing applied.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to a method and apparatus for automaticfabrication of three-dimensional objects from a plurality of individuallayers of fabrication material stacked together in sequence to form theobject. More particularly, the invention relates to the use of asubstrate to convey each layer to a station where these layers areaffixed to each other and then the substrate is removed.

2. Background Discussion

The idea of automated fabrication of three-dimensional solid objectsdates back at least to the 18th century, when a pantograph-like devicewas used in France to copy medallions. James Watt later built severalmachines, based on the same principal, capable of carving full humanbusts. Over the past 45 years, machining, lathe-turning and grindingdevices have been placed under computer control (called “CNC” for“computer-numerical control”) to allow the generation of original shapesfrom designs entered into computers by engineers using computer-aideddesign (CAD) software. These processes are called “subtractive”fabrication, because they start with a solid block of material andgenerate the desired shape by removing material from the block.

Since the subtractive processes work by applying a cutting tool to asolid block, they have the common disadvantage of being limited in theshapes that they can generate. Intricate or nested structures aredifficult or impossible to build by these methods. A more modernapproach is “additive” fabrication in which a fluid or powdered materialis solidified or congealed in successive small regions or layers to formthe desired object. This idea goes back at least to the photo-reliefprocess of Baese (U.S. Pat. No. 774,549), and has been substantiallyrefined through dual-laser photopolymerization of Swainson (DanishPatent Application 3611), liquid droplet deposition of Masters (U.S.Pat. No. 4,665,492), single-laser photopolymerization of Andre (FrenchPatent Application 84 11241) and Hull (U.S. Pat. No. 4,575,330),masked-lamp photopolymerization of Pomerantz (U.S. Pat. No. 4,961,154)and Fudim (U.S. Pat. No. 5,135,379), laser sintering of Feygin (U.S.Pat. No. 4,752,352) and Deckard (U.S. Pat. No. 4,863,538), androbotically guided extrusion of Crump (U.S. Pat. No. 5,121,329).

There are also several hybrid processes which combine additive andsubtractive processes. Usually this involves cutting or etching thecontours of individual layers of an object, and stacking and binding thecontours. The earliest use of such a process is that of Morioka (U.S.Pat. No. 2,015,457), and more recent refinements have been made byDiMatteo (U.S. Pat. No. 3,932,923), Feygin (U.S. Pat. No. 4,752,352),Kinzie (U.S. Pat. No. 5,015,312), and Berman (U.S. Pat. No. 5,071,503).

Sparx AB of Sweden and Schroff Development Corporation of Mission,Kans., have manufactured manual systems which use a substrate to carry asheet of fabrication material bonded to a substrate. Individual layersof material are formed by cutting through the material, removingnegative material, and, prior to affixing successive layers, removingthe substrate. These systems are similar to a Carried-Sheet fabricator,except that their operation is not fully automated and therefore cannotachieve the accuracy, speed, and ease of use of a Carried-Sheetfabricator.

All of the prior additive and hybrid processes suffer from several orall of the following drawbacks:

(1) Accuracy and resolution are limited to the domain of about 0.1millimeters (0.004 inch). One reason is the difficulty of controllingthe action of a laser beam (whether for irradiating, as in Hull orDeckard, or for cutting, as in Feygin), a particle jet (as in Masters),or an extrusion head (as in Crump), plus the difficulty of compensatingfor the width of the laser beam, jet stream or extrusion bead. Anotherreason is the minimum thickness of a single layer that can be formedfrom the raw material liquid or powder, or the minimum thickness of theextrusion bead that can be laid down.

(2) In the fully additive processes, large regions of solid materialtake a long time to fabricate, slowing down the process for buildingstructures with such large solid regions.

(3) All of the processes are difficult and expensive to scale up forfabrication of large objects, because they involve complicatedmechanisms of laser optics or robotics.

(4) All of the processes call for fabrication specifically in very thinlayers, which limits the fabricator speed unnecessarily in cases wheregreat resolution in the vertical direction is not necessary. In manyinstances, fabricator users would like to get a fast, low resolution,rendition of the desired object, but none of the prior art provides away to achieve this.

(5) Only Kinzie and Crump provide a way to achieve a mixture of colorsin the object generated. Kinzie requires a secondary printing process onspecial absorbent or translucent material to achieve this, and Crumprequires the use of specially died materials.

(6) All of the processes always produce a solid object in a permanentlyfixed configuration, such that any fracturing or cross-sectioning of theobject is tantamount to destroying it. No means has ever been providedfor generating an object which can be temporarily taken apart intosections and easily reassembled with no loss of integrity.

(7) The raw materials for most of the processes are specialty chemicalswhich are expensive and, in some cases, are toxic or require specialhandling to prevent combustion.

(8) Many of the processes are limited to working with certain types ofmaterials such as only photopolymers in the simple photocuring methods,or only thermally softenable materials in laser sintering.

(9) Most of the processes hide the object being built in an opaque solidor a murky liquid environment, depriving the fabricator user from thepleasure and benefit of watching the object take shape.

(10) All of the processes, except that of Sparx AB, use complicated andexpensive mechanisms and/or electro-optical devices, making fabricatorsbased on them large, heavy, expensive and difficult to maintain.

The ultimate commercial importance of automatic fabrication ofthree-dimensional objects is hampered by these disadvantages.

SUMMARY OF THE INVENTION Advantages of the Invention

The method and apparatus of this invention has several features, nosingle one of which is solely responsible for its desirable attributes.Without limiting the scope of this invention as expressed by the claimswhich follow, its more prominent features will now be discussed briefly.After considering this discussion, and particularly after reading thesection entitled, “DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS”one will understand how the features of this invention provide itsadvantages, which include:

(1) Accuracy and resolution can both be easily achieved in the domain ofabout 0.05 millimeters (0.002 inch). This can be further reduced to lessthan about 0.01 millimeters (0.0004 inch) with specially accuratecutting or positioning mechanisms and very thin materials.

(2) In several embodiments of this invention in which layers of thedesired object are cut from sheet material, large regions of solidmaterial are fabricated very quickly because they only require cuttingaround the periphery.

(3) In embodiments of this invention in which layers of the desiredobject are cut from sheet material, it is easy to scale up to buildlarge objects. This is because the required mechanisms and componentsare quite simple and, in many cases, are already available for otherpurposes in large size formats.

(4) Thicker layers of materials are used when vertical resolution can besacrificed for speed. This option is analogous to the “draft mode”available on dot matrix printers to achieve fast, low resolution,output. A means (angular cutting) is also provided for ameliorating thisreduction of resolution.

(5) Colors can be easily incorporated and mixed in any desired degree ofcomplexity in the fabricated object. For several embodiments, in whichlayers of the desired object are cut from sheet material, at least 60colors are already available.

(6) In one variation of the method of this invention, fabricated objectsare not permanently fixed, but can be easily separated at any one ormore of many cross sections. The resulting sections can then be easilyrejoined to form again the complete object. The object can be thusseparated and rejoined at the same or different cross sections,repeatedly and without limitation.

(7) For several embodiments of this invention in which layers of thedesired object are cut from sheet material, the raw materials arereadily available and include inexpensive varieties. The materials arenontoxic and have no special handling or storage requirements.

(8) A wide variety of materials may be used in the process, including,metals, plastics, ceramics, and composites.

(9) The method of this invention can be practiced so as to leave theobject being built visible during the fabrication process, providing theuser with the pleasure and benefit of watching the object take shape.

(10) The method can be embodied using simple and inexpensive mechanisms,so that the fabricator equipment can be relatively small, light,inexpensive and easy to maintain.

Methods

The invention includes several methods for fabricating athree-dimensional object.

First Method

In the first method the fabrication material is formed into individuallayers on a carrier substrate. Each layer has a predeterminedconfiguration, and successive layers are stacked in a predeterminedsequence and affixed together to form the object. The layers may vary incurvature, thickness, color, outline, and material composition fromlayer to layer or even within an individual layer.

In one embodiment, the method includes the steps of

(a) providing a stacker, which is a station were the successive layersare stacked together,

(b) forming on a carrier substrate a first layer of fabricationmaterial,

(c) conveying the first layer of fabrication material on said carriersubstrate to said stacker and transferring to a base in said stacker,

(d) separating the carrier substrate from the fabrication material,exposing a bonding surface on said first layer to which successivelayers may be affixed,

(e) forming on the carrier substrate a second layer of fabricationmaterial and conveying the second layer of fabrication material on thecarrier substrate to the stacker,

(f) aligning the second layer in correct position with respect to saidfirst layer and bringing the second layer into contact with the bondingsurface on the first layer so that said layers become affixed togetherin the correct relative position and begin to form a stack,

(g) separating by peeling said carrier substrate from the fabricationmaterial after affixing the second layer to the first layer, exposing abonding surface on the second layer to which other successivefabrication layers may be affixed, and

(h) repeatedly forming and conveying successive fabrication layers onthe carrier substrate in series to the stacker and aligning in correctposition and then affixing the successive fabrication layers to thestack thus being formed and then separating the carrier substrate fromeach successive fabrication layer, until said object is formed as saidstack.

This first method of this invention can be implemented either in anadditive embodiment or in a hybrid embodiment where material is bothadded and subtracted. In the additive embodiment, the method calls fordepositing on the carrier substrate successive layers of fabricationmaterial having a configuration with predetermined boundaries wheresubstantially no material is deposited outside the boundaries.

In the hybrid embodiment, the method calls for dividing the layers offabrication material into a negative region of waste material and apositive region corresponding to the configuration of an individualfabrication layer, and then separating the negative material from thepositive. The fabrication material may be in the form of a sheet offabrication material supported by the carrier substrate, and thepositive and negative regions may be formed by cutting through thematerial but not cutting through the substrate. The negative materialmay be left in place on the substrate when this layer is conveyed to thestacker, and removed along with the substrate when the substrate isseparated from the positive material bonded to the stack. In either anadditive or a hybrid embodiment, an adhesive may be used as a componentof the fabrication material and/or of the substrate. Such adhesivecomponent may participate in the bonding of layers to the stack, and/orit may hold the fabrication material to the substrate but allowing thesubstrate to be separated from the fabrication material when thepositive material of the layer has become affixed to the stack.

Second Method

In the second method the fabrication material is formed into individuallayers, where successive individual layers are stacked to form saidobject. This method includes

(a) providing a station where the successive individual layers areformed into a stack,

(b) placing on a carrier substrate a first layer of fabrication materialcorresponding to the configuration of one individual layer,

(c) conveying the first layer of fabrication material on said carriersubstrate to said station,

(d) prior to separating the carrier substrate selectively inducingbonding of at least a portion of the fabrication material to the stack,and

(d) separating said carrier substrate after bonding said one individuallayer to said stack.

Third Method

The third method includes

(a) providing a station where the successive individual layers arestacked together to form a stack,

(b) placing on a carrier substrate a first layer of fabrication materialand dividing said first layer of fabrication material into a negativeregion of waste material and a positive region corresponding to theconfiguration of one individual layer,

(c) conveying the divided, first layer of fabrication material on saidcarrier substrate to said station,

(d) prior to separating the carrier substrate, including the negativeregion of waste material, from the positive region, selectively inducingbonding of at least a portion of the positive region to the stack, and

(d) separating said carrier substrate, including the negative region ofwaste material, from the positive region after bonding said positiveregion to said stack.

Fourth Method

The fourth method includes

(a) providing a station where the successive individual layers arestacked together,

(b) placing on a carrier substrate a first layer of fabrication materialand dividing said first layer of fabrication material into a negativeregion of waste material and a positive region corresponding to theconfiguration of one individual layer,

(c) conveying the divided, first layer of fabrication material on saidcarrier substrate to said station and transferring to said station,

(d) separating the carrier substrate, including the negative region ofwaste material, from the positive region, exposing a bonding surface onsaid one individual layer to which a successive individual layer isaffixed, said bonding surface including a first region which accepts asecond layer of fabrication material and a second region that interfereswith attaching said second layer of fabrication material to the bondingsurface,

(e) deactivating the second region of the bonding surface prior toaffixing said second layer of fabrication material to the bondingsurface,

(f) placing on the carrier substrate a second layer of fabricationmaterial and dividing said second layer of fabrication material intoanother negative region of waste material and another positive regioncorresponding to the configuration of a successive individual layer, andconveying the divided, second layer of fabrication material on thecarrier substrate to said station,

(g) aligning said individual layers and bringing said bonding surface onsaid one individual layer into contact with said successive individuallayer so that said layers become affixed together,

(h) separating said carrier substrate, including the negative region ofwaste material, from the positive region after affixing said oneindividual layer to said successive layer, exposing a bonding surface onsaid successive individual layer to which another successive fabricationlayer is affixed, and

(i) repeatedly aligning and then affixing successive fabrication layerstogether divided into positive and negative regions after conveying saidsuccessive fabrication layers on the carrier substrate in series to thestation until said object is formed, first affixing individualsuccessive fabrication layers together and then separating the carriersubstrate, including the negative region of waste material, from eachindividual, successive fabrication layer.

Fifth Method

The fifth method calls for an improved way of fabricating athree-dimensional object from fabrication material formed intoindividual layers having a predetermined configuration, where successiveindividual layers are stacked in a predetermined sequence and affixedtogether to form said object. In this improved method a station isprovided where the successive individual layers are stacked together,the successive layers being conveyed to the stacking station on acarrier substrate after dividing individual successive layers into anegative region of waste material and a positive region corresponding tothe configuration of one individual layer, and separating the carriersubstrate, along with the negative region of waste material, from thepositive region, exposing a bonding surface on said one individual layerto which successive individual layers may be affixed. The improvementcomprises selectively deactivating at least a portion of the bondingsurface.

Sixth Method

A sixth method includes

(a) providing a station where the successive individual layers arealigned and affixed together to form a stack having a bonding surface towhich a successive individual layer is affixed,

(b) placing one successive layer of fabrication material on a carriersubstrate carried on a platen positioned next to said station, and

(c) bringing said platen into engagement with the stack to affix the onesuccessive layer to the bonding surface, and

(d) separating said carrier substrate from the one successive layer whensaid one successive layer is affixed to the bonding surface by movingthe platen to pull incrementally the carrier substrate from the stack.

In this sixth method substantially all of the fabrication material ineach layer is affixed to the stack prior to removing the carriersubstrate. A portion of the fabrication material in one layer is affixedto the stack, but before all the fabrication material in said one layeris affixed, a portion of the carrier substrate is removed. Thefabrication material is affixed to the stack at the same time thecarrier substrate is being removed. In this sixth method the platen hasa face with (a) a constant single curvature, (b) a flexible curvature,or (c) a controlled curvature. The carrier substrate is releasably heldto the platen, with the layer of fabrication material on the carriersubstrate placed on the platen uniformly to avoid entrapment of airbetween the carrier substrate and the platen, so that the layer offabrication material does not wrinkle or buckle.

Seventh Method

A seventh method for fabricating a three-dimensional object comprisesautomatically forming a stack of layers corresponding to the object bystacking said layers in a predetermined sequence. The individual layerseach are first formed into a predetermined two-dimensional configurationas required to form the object, with at least some of the layers havinga non-flat shape. Preferably, there is a base supporting the layers.This base has a curved surface, and at least one of the layers is placedon the curved surface of the base, so that the one layer has a non-flatshape conforming to the curved surface of the base. The base element maybe placed at the bottom of the stack or between layers. In this seventhmethod, from layer to layer the size of the layers are different tocreate a curvature as subsequent layers are overlaid.

Eighth Method

An eighth method comprises stacking a plurality of layers together in apredetermined sequence and affixing them together to form the object, atleast some of the layers being formed from a pliable material havingthicknesses which vary as mathematical functions of the surface extentof the layers, where said mathematical functions are calculated toaccommodate the curvature said individual layers will assume in thestack, such curvature causing the thickness of the layer to change whenstacked. The layers are conveyed to a stacking station on a carriersubstrate, each layer preferably having the ability to adhere to a stackof previous layers. There may be an interstitial base element placedbetween layers of material or from layer to layer the size of the layersare different to create a curvature as subsequent layers are overlaid.

Ninth Method

A ninth method includes

(a) providing a station were the successive individual layers arestacked together,

(b) forming on a surface of one or more carrier substrates a series oflayers of fabrication material corresponding to the configuration ofindividual layers by extruding the fabrication material through a nozzleguided over said surface of a carrier substrate,

(c) conveying said layers of fabrication material on a carrier substrateto said station,

(d) aligning layers and bringing each of said individual layers intocontact with a successive individual layer so that said layers becomeaffixed, and

(e) separating the carrier substrate from the individual layers offabrication material, exposing a bonding surface to which a successiveindividual layer is affixed.

Tenth Method

A tenth method calls for individual layers to be stacked in apredetermined sequence and affixed together to form the object withminimal layer-to-layer graininess. This method includes

(a) forming said individual layers with edges that slope in a mannerthat minimizes layer-to-layer graininess upon stacking the successivelayers on top of each other, said edges forming corners with thesurfaces of the layers, and

(d) stacking said individual layers together in a predetermined mannerwith the corners of one edge meeting the corners of the edges of boththe previous layer and the next following layer, whereby layer-to-layergraininess is minimized.

Eleventh Method

An eleventh method calls for at least two of layers being bonded by aprocess which is capable of being released and reactivated, so that theobject may be separated into sections along an interface between saidtwo layers and easily reassembled.

Twelfth Method

A twelfth method is draft mode. In this method, each of the layers has apredetermined thickness which is several times thicker than thethickness of the layers needed to attain normally acceptable resolution.These thicker layers reduce the layer-to-layer resolution of the objectbut enable the object to be fabricated at a substantially higher speedthan that attainable at normally acceptable resolution. The thickness ofthe layers to attain normally acceptable resolution is from 0.01 to 25millimeters, and each of the layers has a predetermined thickness atleast 3 times the thickness to attain normally acceptable resolution.

Apparatus

In general, the apparatus includes a formation station where successivelayers of fabrication material are formed on a carrier substrate andthen conveyed to a stacker where they are separated from the substrateand bonded together to form the desired three-dimensional object. Thefollowing are some of its major features. Other features are discussedin the section “Detailed Description Of The Preferred Embodiments.”

The first feature of the apparatus of this invention is the formationstation where the successive, individual fabrication layers are formedon successive carrier substrates. The layers of fabrication materialeach have a predetermined configuration, and successive layers arestacked in a predetermined sequence and affixed together to form theobject at a stacker. The substrate and fabrication material may be inthe form of a sheet and there may be an adhesive component of thefabrication material and/or of the substrate which participates in thebonding of the layers to the stack and/or holds the fabrication materialto the substrate but allows the substrate to be separated from thefabrication material when the positive material of the layer has becomeaffixed to the stack.

The second feature is that a deposition mechanism may be used to depositon a carrier substrate a fabrication material to form successive layers,each successive layer having a configuration with predeterminedboundaries, with substantially no material deposited outside saidpredetermined boundaries.

In an alternate embodiment, a fabrication material may be supplied inthe form of a sheet on a substrate, and a cutter may be used to cutthrough the fabrication material, but not though the substrate, todivide the fabrication material into a negative region of waste materialand a positive region corresponding to the configuration of anindividual layer. In one embodiment, a waste material removing mechanism(“weeder”) removes the negative material from a layer prior to conveyingthe layer to the stack. The negative material may alternatively remainon the substrate until after the layer is adhered to the stack, and whenthe substrate is separated the negative material adheres thereto and isthereby removed.

The third feature is a conveyor for conveying in the predeterminedsequence the successive fabrication layers on the successive carriersubstrates from the formation station to the stacker. An alignmentmechanism aligns the successive fabrication layers so that eachsuccessive fabrication layer is in the correct position with respect tothe stack.

The fourth feature is that successive carrier substrates may be sectionsof a continuous belt which travels along a predetermined path past theformation station and stacker. There are means for placing onto the beltin advance of the stacker fabrication material corresponding to thephysical dimensions of an individual layer. If the fabrication materialis cut into positive and negative regions, there are means fortransferring the positive material to the stacker and for removing thenegative material prior to placing onto the belt a successive layer offabrication material. Instead of a continuous belt, the substrate may bea series of individual sheets, sections of a roll of material, or asingle plate used repeatedly, or a revolving set of such plates.

The fifth feature is a separator which separates each successive carriersubstrate from the fabrication layer thereon to expose a bonding surfaceon each fabrication layer. An affixing mechanism brings each successivefabrication layer conveyed to the stacker into contact with the stack,allowing or inducing the new layer and the stack to bond to each other.

The sixth feature is that the separator separates each successivecarrier substrate from the fabrication layer thereon after affixation ofthis layer to the stack.

The seventh feature is a weeder mechanism which selectively removes thenegative region of waste material from the carrier substrate. The weedermechanism, which is in advance of the stacking station, may include apick-up film which selectively contacts the negative region of wastematerial. The weeder mechanism may also include a device whichselectively treats at least a portion of the negative region of wastematerial to render the selected portion susceptible to adhesion to thepick-up film which subsequently contacts the negative region of wastematerial. The weeder mechanism may include a barb element thatselectively engages and retains a negative region of waste materialuntil the retained negative region of waste material is removed from thebarb element.

An eight feature is the use of a continuous roll of carrier substratehaving thereon a continuous layer of fabrication material, and aformation station where successive, individual fabrication layers areformed on the carrier substrate by dividing successive segments of thecontinuous layer of fabrication material into a negative region of wastematerial and a positive region corresponding to the configuration of oneindividual layer. There is a stacking station where the positive regionsof the successive segments of the continuous fabrication layer aresequentially stacked to form the object, and a conveyor conveys thesuccessive segments formed at the formation station to said stackingstation on the continuous carrier substrate. An affixing and separatingmechanism affixes said positive region to a stack of layers at thestacking station and separates the positive region of each successivesegment from the carrier substrate. A portion of the continuous carriersubstrate between the formation station and said stacking station ismaintained by said conveyor in a slack state.

A ninth feature is that the affixing and separating mechanism includes aplaten device about which the sheet material is wrapped. The platendevice is moved along a path adjacent the stack, bearing against thestack to deposit the fabrication material onto the stack. The platendevice as it moves along the path retains on the platen device thesubstrate.

The tenth feature is employing a flexible sheet member comprising asubstrate and a fabrication material having an exterior surface and aninternal surface carrying an adhesive which bonds the fabricationmaterial to the substrate but allows the substrate to be removed toexpose the adhesive upon separation of the substrate from thefabrication material. A cutter in advance of the stacking stationpartially severs the sheet member, cutting through the fabricationmaterial but not the substrate to form on the substrate a positiveregion corresponding to a predetermined configuration for an individuallayer of fabrication material and a negative region of waste material.An affixing and separating mechanism at said stacking station receivesthe sheet material from the cutter and separates each successive carriersubstrate from the individual fabrication layer thereon to expose theadhesive on said internal surface of the individual fabrication layer.This affixing and separating mechanism includes a roller device aboutwhich the sheet material is wrapped. The roller device is moved along apath adjacent a previously stacked fabrication layer which has itsadhesive bearing, internal surface exposed, bearing against thepreviously stacked fabrication layer to deposit the fabrication materialcarried by the roller device on said exposed, adhesive bearing, internalsurface of said previously stacked fabrication layer, with the adhesiveon said internal surface of said previously stacked fabrication layerbonding to said exterior surface of the individual fabrication material.The roller device as it moves along the path retains on the rollerdevice the substrate, and any negative region adhering thereto, toexpose the internal surface of the individual fabrication material beingdeposited so that a successive fabrication layer may be bonded thereto.The roller device is first moved in one direction to deposit the sheetmaterial, including both the substrate and the individual fabricationlayer thereon, on the previously stacked fabrication layer, and thenmoves in an opposite direction to separate the substrate and anynegative region of waste material thereon from the deposited fabricationlayer.

The eleventh feature is that the affixing and separating mechanismincludes a roller device which is moved along a path adjacent the stack.The roller device bears against the sheet member so that the exteriorsurface of the fabrication material contacts the exposed adhesive,bonding to the stack. The roller device as it moves along said pathpulls the substrate, and any negative region adhering thereto, from theindividual layer to expose its internal surface so that successivefabrication layers may be bonded thereto. The roller device is moved ina sequence so that the exterior surface of the individual fabricationlayer is bonded to the stack prior to separation of the substrate fromsaid individual fabrication layer. The roller device moves first to bondselectively the individual fabrication material to the stack and movesagain to pull the substrate, and any negative region adhering thereto,from said individual fabrication layer bonded to the stack. The rollerdevice may include a set of spaced apart parallel rollers. The rollersincludes a gripper mechanism which grips an edge of the sheet member andpulls the substrate, and any negative region adhering thereto, from thestack. Preferably, a waste material removing mechanism removes, at leastpartially, the negative region of fabrication material from thesubstrate prior to the affixation of the layers.

The twelfth feature is a fabrication material removal mechanism inadvance of the stacking station which selectively removes substantiallyall of interfering negative region from the substrate prior to stackingof the individual fabrication layers. A separator separates from thefabrication layers each successive, individual carrier substrate withany remaining non-interfering negative region remaining thereon afteraffixation of the previous individual fabrication layer to the nextsuccessive fabrication layer. A gripper mechanism grips an edge of asubstrate and pulls the substrate, and any negative region adheringthereto, from stacked layers affixed together.

BRIEF DESCRIPTION OF THE DRAWING

The preferred embodiments of this invention, illustrating all itsfeatures, will now be discussed in detail. These embodiments depict thenovel and non-obvious methods and apparatus of this invention shown inthe accompanying drawing, which is for illustrative purposes only. Thisdrawing includes the following figures (Figs.), with like numeralsindicating like parts:

FIG. 1 is a flow chart illustrating the Conveyed-Adherent process ofautomated fabrication, the fabrication method of this invention.

FIG. 2(a) is a perspective view of an example fabricated object, acoffee cup, made according to the method of this invention using theapparatus depicted in FIG. 6A.

FIG. 2(b) is a cross-sectional view taken along line 2B—2B of FIG. 2(a).

FIG. 2(c) is a side view of the cup shown in FIG. 2(a) using portions ofnegative material as a support for the handle of the cup.

FIG. 3(a) is an enlarged, cross-sectional view of a fabrication medium,showing fabrication material being supported by a substrate that carriesthe material to a stacker.

FIG. 3(b) is a cross-sectional view similar to that shown in FIG. 3(a),where the fabrication material comprises sublayers, where one sublayermay be a primary fabrication material and another sublayer may be anadhesive material.

FIG. 3(c) is a cross-sectional view of a stack consisting of severallayers of fabrication material bonded together, including layers betweenwhich there is negative overlap.

FIG. 4(a) is a cross section of a stack showing one way of varyingcurvature of layers.

FIG. 4(b) is a cross section of a stack showing a second way of varyingcurvature of layers.

FIG. 4(c) is a cross section of a stack showing a third way of varyingcurvature of layers.

FIG. 4(d) is a cross sectional view of a sheet of fabrication materialposition on a curved support or stack.

FIG. 4(e) is a side elevational view of a layer used to achieve thecurvature depicted in FIG. 4(d).

FIGS. 5, sub parts (a) through (g) are a series of cross-sectional viewsof a stack illustrating weeding theory.

FIG. 6A(a) is a perspective view of an example Carried-Sheet fabricatorused to form and assemble the layers of fabrication material. In thisexample fabricator, the fabrication medium is supplied on rolls.

FIG. 6A(b) is a side view of the fabricator shown in FIG. 6A(a).

FIGS. 6B(a) through (c) show several subsystems of the exampleCarried-Sheet fabricator of FIGS. 6A(a) and (b), where FIG. 6B(a) is aside view of the cutter assembly of the fabrication unit shown in FIG.6A(a), FIG. 6B(b) is a perspective view of the stacker of thefabrication unit shown in FIG. 6A(a), and FIG. 6B(c) is a perspectiveview of the roller assembly of the stacker shown in FIG. 6B(b).

FIGS. 6C, sub parts (a) through (e), are cross-sectional views of theaction sequence of the stacker of FIG. 6B(b), where FIG. 6C(a) shows asegment of fabrication medium initially advancing into the stacker, FIG.6C(b) shows the fabrication medium aligned in correct position withrespect to a stack of previously aligned and bonded layers offabrication material, FIG. 6C(c) shows the roller assembly moving acrossthe aligned fabrication medium in order to transfer the positivematerial from the fabrication medium to the stack (the substrate andnegative material on its surface are wound up on one of the rollers ofthe roller assembly), FIG. 6C(d) shows the completion of the transfer offabrication material to the stack, and FIG. 6C(e) shows the rollerassembly returning to its starting position.

FIGS. 7A, sub parts (a) through (c), schematically illustrate oneembodiment of a weeder.

FIGS. 7B, sub parts (a) through (f), schematically illustrate anotherembodiment of a weeder for small regions.

FIG. 8 schematically illustrates selective adhesion activation.

FIG. 9(a) and FIG. 9(b) are perspective views of the cup shown in FIG.2(a) schematically illustrating selective adhesion neutralization onexposed surfaces.

FIGS. 10A, sub parts (a) through (j), are cross-sectional views of theaction sequence of an arc platen applying a layer of fabricationmaterial to a stack using the method of consequent peel-off with oneholding platen.

FIGS. 10B, sub parts (d) and (e), are cross-sectional views of theaction sequence of an arc platen applying a layer of fabricationmaterial to a stack using the method of simultaneous peel-off with oneholding platen platen. Sub parts (a) through (c), and sub parts (f) and(g) are identical to the corresponding sub parts (a) through (c) and (f)and (g) of FIG. 10A.

FIGS. 10C, sub parts (a) through (d), are cross-sectional views of theaction sequence of a system of rollers applying a layer of fabricationmaterial to a stack using the method of consequent peel-off with atwo-platen system.

FIG. 10D is a cross-sectional view of a stacker employing delayedpeel-off with a multi-platen system.

FIGS. 10E, sub parts (a) through (e), are cross-sectional views of theaction sequence illustrating simultaneous peel-off with a single roller.

FIGS. 11A, sub parts (a) through (f), depict variations on platen designhaving a constant single curvature, where FIG. 11A(a) is a perspectiveview of a roller (cylindrical platen); FIG. 11A(b) is a perspective viewof an arc platen; FIG. 11A(c) is a perspective view of a wing platen;FIG. 11A(d) is a perspective view of a bar platen, FIG. 11A(e) is aperspective view of a blade platen; and FIG. 11A(f) is a perspectiveview of a a roller platen mounted for vertical and horizontal movement.

FIG. 11B, sub parts (a) through (d), are cross-sectional views of theaction sequence of the operation of a peel-off bar.

FIG. 11C, sub parts (a) through (c), are side views of the actionsequence of the operation of a pillow platen.

FIG. 11D, sub parts (a) and (b), are perspective views of a sausageplaten.

FIG. 11E, sub parts (a) and (c), are side views of the action sequenceof the operation of a flat platen with controlled curvature, and subpart (b) is a plan view of the platen shown in sub parts (a) and (c).

FIG. 12, sub parts (a) through (l), illustrate various devices forholding a fabrication medium to a platen.

FIG. 13 is a schematic view illustrating an alternate type ofCarried-Sheet fabricator using an endless belt substrate to convey thefabrication material to the stacker.

FIG. 14 is a schematic view of an example of a Carried-Sheet fabricatorusing continuous take-up of scrap.

FIG. 15 is a schematic view illustrating an example of an additiveConveyed-Adherent fabricator using a deposition device to depositfabrication material on an endless belt substrate.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Method

The flow chart of FIG. 1 depicts the method of this invention, whichincludes the three primary operations of mathematical modeling,formation of layers, and affixing of the layers. As depicted in FIG. 2,a three-dimensional object such as a cup 10 may be fabricated fromsuccessive stacked and bonded layers of fabrication material 11 (FIG.3(c)). Individual layers are formed from the fabrication material 11,each layer having the required dimensions and contour so that whenstacked together in sequence they form the cup 10. These layers arealigned in correct relative position and affixed together in sequence toform the base 10 d, walls 10 a, and handle 10 b of the cup 10 shown inFIG. 2(a). FIG. 2(c) shows some support structures 10 c used to supportthe handle 10 b of the cup 10. After fabrication, these supportstructures 10 c are removed.

I Mathematical Modeling

A mathematical model of the object is made, where a data representationof the desired three-dimensional object is ordered in a set of numericalrepresentations of layers which, together, represent the whole object.In other words, a series of data packages, each data packagecorresponding to the physical dimensions of an individual layer offabrication material, is stored in the memory of a computer in logicalsequence so that the data packages correspond to individual layers offabrication material stacked together to form the object.

Creation of data packages. Prior to formation of the layers from thefabrication material, the geometry of the desired three-dimensionalobject is logically divided into a sequence of mutually adjacenttheoretical layers, with each theoretical layer defined by a thicknessand a set of closed, non-intersecting curves lying in a smoothtwo-dimensional surface. These theoretical layers, which exist only asdata packages in the memory of the computer, are referred to as “logicallayers.” In the simplest circumstance, each two-dimensional logicallayer will be a plane so that each layer will be flat, and the thicknesswill be the same throughout any particular layer. However, this is notnecessarily so in every case, as a layer may have any desired curvatureand the thickness of a layer may be a function of position within itstwo-dimensional surface. The only constraint on the curvature andthickness function of the logical layers is that the sequence of layersmust be logically adjacent. This means that, in considering two layersthat come one after the other in the sequence, the mutually abuttingsurfaces of the two layers must contact each other at every point,except at such points of one layer where the corresponding point of theother layer is void of material.

The data packages for the logical layers may be created by any ofseveral methods:

(1) For a three-dimensional computer-aided design (CAD) model, bylogically “slicing” the data representing the model,

(2) For topographic data, by directly representing the contours of theterrain,

(3) For a geometrical model, by representing successive curves whichsolve z= constant for the desired geometry, and

(4) Other methods appropriate to data obtained by computer tomography,satellite reconnaissance, laser digitizing, line ranging, or othermethods of obtaining a computerized representation of athree-dimensional object.

Various techniques for carrying out the mathematical modeling arediscussed in depth in Chapter 5 of Computer-Aided Design andManufacturing by Farid M. L. Amirouche, Prentice Hall, 1993, and CADModeling and Alternate Methods of Information Transfer for RapidPrototyping by Richard J. Donahue and Robert S. Turner in proceedings ofthe Second International Conference on Rapid Prototyping, University ofDayton, 1991.

Interactive processing of logical layers. An alternative to calculatingall of the logical layers in advance is to perform measurements of thedimensions of the growing object as each new layer is bonded, and to usethis information to help in the determination of where each new logicallayer of the object should be, and possibly what the curvature andthickness of each new layer should be. This will often result in moreaccurate final dimensions of the fabricated object because the actualthickness of a sequence of bonded layers may be different than thesimple sum of the intended thicknesses of the individual layers.

Positive and negative regions. A set of closed, non-intersecting curvesthat are part of the definition of each layer unambiguously divide asmooth two-dimensional surface into two distinct regions. (“Region” doesnot mean a single, connected area. Each region may consist of severalisland-like subregions that do not touch each other.) One of theseregions is the intersection of the surface with the desiredthree-dimensional object, and is called the “positive region” of thelayer. The other region is the portion of the surface that does notintersect the desired object, and is called the “negative region.” Thesecurves are the boundary between the positive and negative regions, andare called the “outline” of the layer. Fabrication material which liesin a positive region is “positive material,” while fabrication materiallying in a negative region is “negative material.” The definition of alayer may also include other curves, such as curves which form theboundary between different materials or curves which indicate wherenon-boundary cuts or other operations are to be performed on fabricationmaterial.

II Formation of Layers

The data packages are stored in the memory of the computer, whichcontrols the operation of the fabrication equipment. Using these datapackages, the computer controls automated formation equipment tomanipulate the fabrication material to form on the surface of asubstrate a layer of material in accordance with the specifications of adata package. The fabrication material used to form the layers has theproperty that layers brought into contact bond to each other. Possibly,the material may require ancillary treatment to have the desired bondingcharacteristic.

Properties of the fabrication material. It is not necessary that thedeposited material have structural integrity upon being deposited. Itshould be capable of forming a layer which maintains the desired patternand thickness on the substrate during conveyance, and is capable ofassuming a state of structural integrity when bonded to the stack. Forexample, the deposited material may be a powder or a gel which, ifshaken vigorously, might fall off the substrate or become smeared, butwhich, protected from shaking, remains in place on the substrate.Furthermore, the fabrication material may or may not be homogeneous. Itmay, for example, exhibit variations in composition based upon thestructural requirements of the desired object being built. Thesevariations may serve to accomplish internal variations of the physicalproperties of the object, such as hardness, mass density, coefficient ofthermal expansion, color, etc. Another case in which the fabricationmaterial may be inhomogeneous would be one in which the fabricationmaterial consists of a stratum of a primary material and a stratum ofadhesive material. In this example, the primary material would providethe gross physical characteristics of the object, while the adhesivewould generally provide bonding between the layers, although theadhesive can also contribute to the overall characteristics.

Fabrication raw materials. The raw materials that can be used to formthe layers include various types and combinations of metals, plastics,ceramics, and composites, such as:

(a) Hardenable pastes and gels, including (i) common adhesives, such asElmers® glue from Borden Inc. of Columbus, Ohio, (ii) metal or ceramicpowders or whiskers suspended in a polymer matrix, such as Fodel® andFormon® thick film compositions from DuPont of Wilmington, Del., (iii)sol-gel derivatives, such as ormosils (organically modified silicates),and ceramers, and (iv) other formulations of pastes and gels.

(b) Molten metals, thermoplastics, and ceramics, which harden byfreezing.

(c) Plastic resins that harden by various means, such as photonic,thermal, electrostatic, and other means.

(d) Other soft or fluid materials which are hardenable or fusible byvarious means,

(e) Sheets of plastic, wax (including investment casting wax), foam,linoleum, fabric (including open-weave fabric), paper (includingcardboard and corrugated cardboard), cork, metal (including metal foiland tape-cast metal), ceramic (including tape-cast ceramic), orcomposite prepreg.

(f) Plastic, foam, metal, paper, ceramic, or other sheets with adhesivecoating, such as Calon® II cast vinyl film from Arlon of Santa Ana,Calif., ScotchCal™ films from 3M Company of St. Paul, Minn., sandblaststencil material from Anchor Continental, Inc. of Columbia, S.C.,ISODAM® elastomeric sheets from E-A-R Specialty Composites ofIndianapolis, Ind., Spar-Cal™ Metal Mend aluminum foil or Spar-Cal™Chrome Brite aluminum foil from Spartan International, Inc. of Holt,Mich., and Fasson™ label paper from Avery Dennison Corporation ofPasadena, Calif.

(g) Sheet materials that engage in bonding without the use of anadhesive, such as the cohesive vinyl used in the manufacture ofStik-ees® glueless plastic decals by Stik-ees® of Vista, Calif., orKoroseal® flexible magnetic sheeting from RJF International Corporationof Cincinnati, Ohio.

(h) Various combinations of plastic, metal, or ceramic sheets, strips,and/or filaments with molten, thermosetting, or other type of binder ormatrix material.

(i) Other appropriate combinations of materials.

Methods of varying material composition. If variation of the compositionof the fabrication material is desired within any particular layer, andif the mechanism for depositing the fabrication material has thecapability of depositing the required various compositionsautomatically, then the variation in composition may be representedmathematically within the data package for each layer, and themathematical representation used to control the composition of materialdeposited. However, if the mechanism for depositing the fabricationmaterial is limited to providing layers of any one specific compositionat a time, then variations in composition may be accomplished bylogically separating a particular layer into sublayers, where eachsublayer is composed of a different material, and the union of thesublayers is equal to the particular layer. Each sublayer is thentreated as a distinct layer in the fabrication process, and the completelayer is formed by the formation and bonding of a succession of itsconstituent sublayers. If the interface between sublayers is alongsurfaces perpendicular to the layers, and not along surfaces parallel tothe layers, then the bonding of each sublayer is not to the previoussublayer, but to the previous complete layer.

Methods of Varying Curvature of Layers. In an object made of curvedlayers, one often wants the curvature to vary from layer to layer. FIGS.4(a), (b) and (c) illustrates three ways to accomplish this. FIG. 4(a)shows a stack 66 consisting of five layers in which the second andfourth layers (counting from the bottom) consist of shorter segmentsseparated by gaps 66 a. When the material of the third and fifth layersis laid down, it curves around these segments and falls into the gaps.In this way the third and fifth layers become curved. FIG. 4(b) shows astack 66 consisting of six layers in which the first and third layershave uniform thickness, while the other layers have variations in theirthicknesses. When a layer has nonuniform thickness, the curvature of itstop surface is different than the curvature of its bottom surface. Thedifferences in curvature build up from layer to layer, inducingcurvature in all higher layers in the stack, as seen in this figure.FIG. 4(c) shows a stack 66 in which all layers are continuous (no gaps)and all layers are of uniform thickness, but an interstitial base 364has been inserted on top of the second layer before laying down thethird layer. Interstitial base 364 induces curvature in the third layerand thereby in all subsequent layers. Interstitial base 364 may beinserted on stack 66 (after lay-down of the second layer) eitherautomatically according to preprogrammed computer instructions, ormanually upon pausing of the fabricator to wait for this manualinsertion to be performed.

“Draft Mode” fabrication. Depending on the method of depositing thefabrication material, the fabrication process will often go faster ifthe layers are thicker. However, thicker layers reduce thelayer-to-layer resolution of the fabricated object. Thus, there is atrade-off between speed and layer-to-layer resolution. This trade-offcan be used to advantage by building initial rough models of the desiredthree-dimensional object quickly, and then reducing the layer thicknessas the design becomes more certain and a more careful representation isdesired. This is similar to the option provided in dot matrix printersbetween “draft mode” and “correspondence mode” printing.

Description of the substrate. If the layers are flat or singly curved,then the substrate may be a simple sheet material, such as paper,plastic or metal. In this case, the substrate may be, for example, aseparate segment for each layer, or it may be a long roll on whichfabrication material has been deposited in advance, or it may be acontinuous roll that is cycled through the fabrication equipment toserve over and over again for new layers. If, however, the layers havemore complicated curvature, then the substrate must be a flexiblematerial, capable of assuming the correct curvature and imposing thatcurvature on the fabrication material. For example, the substrate mayhave a structure resembling that of crepe paper, and be attached to asystem of robotically controlled fingers capable of manipulating itsshape. In another example, the substrate may be a sheet of plastic witha great tolerance for stretching, and be attached to a system ofelectromagnetically controlled rods that push and pull on it to createthe desired shape. The curvature of the substrate may be set prior tothe deposition of the fabrication material on it, or the fabricationmaterial may be deposited first and the substrate later contorted intothe desired curvature. The curvature of the stack may be used, when thenew layer is brought into contact with it, to establish the curvature ofthe new layer, but the substrate must be capable of yielding to andassuming this curvature in order to maintain the relative position ofthe parts of the new layer as it is being brought into contact with thestack.

Accommodating thickness of layers to changes in curvature. If thesubstrate assumes the correct curvature of the new layer prior to thedeposition on it of the fabrication material, then the fabricationmaterial may be deposited in the correct final thickness of the layer.If, however, the curvature of the substrate is to change afterdeposition on it of the fabrication material, then the thickness withwhich the fabrication material is deposited must be calculated such thatthe layer will assume the correct thickness when it is contorted intothe correct curvature. In the simplest circumstance, where the layersare flat, the fabrication material is simply deposited in a uniformthickness for each layer.

FIG. 4(d) shows a cross section of a layer of fabrication material 11 asit might lie after being affixed to a stack. This layer is shown to haveapproximately uniform thickness and to be nearly flat near the edges,but have considerable corvature near the center. FIG. 4(e) shows anexample of a layer that could be formed in order to yield the finalshape and thickness shown in FIG. 4(d). In FIG. 4(e), the layer isformed on a flat substrate so that it's bottom surface is flat. Thecenter region of the layer is formed with a greater thickness than theedge regions becasue when the layer is bent into the correct final shapeshown in FIG. 4(d) the material in the center region will become spreadout due to the stretching induced by the curvature. This spreading outcauses the material in the center region to become thinner after beingbent into shape than it was when it was lying flat. A Mathematicalcalculation may be performed to determine the correct thickness todeposit at each point on the substrate in order to yield the correctfinal thickness at each position after the layer takes on the correctfinal shape. Such a mathematical description is called a “function”. Itmay be desireable to calculate such a mathematical function for eachlayer which I will assume on the stack a curvature which if differentfrom the curvature in which it was formed.

Method of depositing fabrication material. The fabrication material maybe deposited on the substrate by any of several methods, such as:

(1) Spraying in the proper pattern and thickness, as with an ink jetmechanism.

(2) Extruding the material through a nozzle robotically guided over thesurface of the substrate to form the proper pattern and thickness.

(3) Using a laser printer to deposit fabrication material on alaser-printable image transfer film, such as Press-n-Peel™ from TechniksInc. of Ringoes, N.J. This transfer film can be run through a laserprinter, and accepts an image from the printer just as a piece of paperdoes. However, the film is designed to allow the image to be removedfrom the film by the application of heat. In this technique, the filmserves as the substrate, a laser printer mechanism forms the individualfabrication layers, and a heating element in the stacker is used toeffect the transfer of the fabrication material from the transfer filmto the stack.

(4) Coating of the substrate with the desired material, followed bycutting through this coating in the pattern of the closed curves in thelogical layer. The cutting may be accomplished by a knife blade, a laserbeam, a heated element, a fluid jet, or any other means capable ofcutting the material cleanly without cutting so far into the substrateas to damage the structural integrity of the substrate. After cutting,the material lying on the substrate that is not to be part of thedesired object (the “negative material”) may be removed from thesubstrate or it may be left in place to be removed by “substrateweeding.” These options are described below under Weeding.

(5) Or any other means or process capable of distributing the desiredmaterial in the desired pattern and thickness on the substrate.

The method of depositing the fabrication material is an automaticprocess acting under instructions based on the data packages of thelogical layers. For some materials, it is possible to buy thefabrication material already coated on a substrate, in which case it isonly necessary to cut the outline of the layer into the material. Someexamples of such materials include adhesive-backed foams and films, suchas Calon® II cast vinyl film from Arlon of Santa Ana, Calif., ScotchCal™films from 3M Company of St. Paul, Minn., and sandblast stencil materialfrom Anchor Continental, Inc. of Columbia, S.C.

Reducing layer-to-layer “graininess”. Some methods of depositingfabrication material may allow control of the slope of the edges of thefabrication material deposited. For example, when cutting a pattern in acoating on the substrate, the cutting implement may be rotated to cut onan angle so that the edge surface of the material is not perpendicularto the large surfaces. If the edge is made with a slope such that, afterbonding, the corners of the edge meet the corners of the edges of boththe next previous layer and the next following layer, then the resultmay be a smoother surface than if the edge were made perpendicular.

Weeding. In a Carried-Sheet fabricator (a Conveyed-Adherent fabricatorof the hybrid variety) one must separate the negative material from thepositive. Borrowing from sign-cutting terminology this may be called“weeding” because it is the removal of unwanted material. The boundarybetween the positive and negative materials is established by thecutting process. After a boundary is cut, one has a choice. One mayremove the negative material from the substrate before conveying thesubstrate to the stack. Because this is done by a special mechanism, itis called “mechanical weeding.” Alternatively, one may in certaincircumstances leave the negative material on the substrate so that it isconveyed to the stacker along with the positive material. Thecircumstances in which this is permissible are when one knows forcertain that the positive and negative material will separate when thesubstrate is peeled away from the stack, with the positive materialadhering to the stack and the negative material remaining on thesubstrate. This method of separating out the negative is called“substrate weeding.”

There are several factors that can hamper weeding, such as (a) negativeoverlap, in which the negative region of the current layer touches somepart of the stack, (b) cross-boundary linking, which is caused bymolecular interactions between the positive and negative material acrossa cut line, (c) friction or collision of edges, where the edges of thenegative and positive material rub against or catch on each other, (d)an error in alignment of a layer with respect to the stack, which cancause negative overlap to occur in a case where it should not, and (e)shear forces imparted on the fabrication material by the platen system.

In negative overlap, the negative region of the current layer touchessome part of the stack, so that the corresponding negative material, ifnot specially handled, might adhere to the corresponding part of thestack. If the adhesive contact is strong enough to pull the negativematerial off the substrate, this defeats substrate weeding.

FIG. 3(c) illustrates negative overlap. Layers e and f do not exhibitany negative overlap, and these layers are therefore good candidates forsubstrate weeding. Each of layers b, c, and d has a negative region thattouches the material of the layer below it in the stack. For layers band d this contact is substantial and most likely requires specialprocessing, such as mechanical weeding or selective adhesionneutralization. Layer c is a borderline case since its negative regionhas a small overlap c′ with the underlying positive region of layer b.Whether this small region of overlap requires special processing dependson the strength of adhesive contact developed between the negativematerial and the stack and on how this adhesive contact compares withthe adhesive contact between the negative material and the substrate 13.

Another illustration of negative overlap is provided in FIGS. 5(a)through 5(g). In building the coffee cup 10, negative overlap arises inthe bottom layer 10 a′ of the walls 10 a of the cup, which is the firstlayer above the top layer 10 d′ of the base of the cup, as shown in FIG.2(b). The correct fabrication of this portion of the cup is shown inFIG. 5(a), where the new fabrication material 262 of the bottom layer ofthe walls is shown properly affixed to the stack 66 of layersconstituting the base of the cup. In this correct procedure, theinterior of the walls 10 a is void of material. However, if the newlayer is simply cut and placed on the stack in the correct position, asshown in FIG. 5(b), then the negative material 17 in the interior of thewalls will adhere to the stack 66, and will not come off by substrateweeding. When substrate 13 is peeled from stack 66, portion 17 c′ of thenegative material is properly substrate weeded, portion 17 c″ remainsadhered to the stack in error, as is shown in FIG. 5(c). FIG. 5(b) andFIG. 5(c) therefore illustrate an incorrect procedure. The problem withnegative overlap is that it can interfere with substrate weeding. Theways to deal with this problem include mechanical weeding (FIG. 5(d) andFIG. 5(e)) and selective adhesion neutralization (FIG. 5(f) and FIG.5(g)).

In mechanical weeding, selected negative material 17 is mechanicallyremoved from substrate 13, leaving void 17 d, as shown in FIG. 5(d).(Example devices for performing this function are illustrated in FIG. 7and explained below.) When overlapping negative material has beenremoved by mechanical weeding and then the fabrication medium 34 isconveyed to the stacker, substrate weeding is able to work on remainingnegative material 17 c′, and the proper void 17 d is left in the placeof the overlapping negative material, as shown in FIG. 5(e).

Selective adhesion neutralization refers to an action taken on eitherthe overlapping negative material 17 or the portion of the top layer ofthe stack 66 with which it overlaps, which action reduces or eliminatesthe adhesive interaction between the materials. FIG. 5(f) shows anadhesion neutralizer 145 acting on the problem portion of the top layerin this way. The neutralizer is mounted on an automatic device (notshown) that aims it so as to neutralize a selected region (e.g. a regionoverlapped by a negative region of the next layer). The neutralizingaction might consist of coating over the surface of a tacky material, ordepositing a reagent that causes a tacky component to cross-link andtherefore loose its tack, or irradiating a material to stimulatecross-linking, or applying an agent and/or action (such as rubbing) tothe surface of a material to remove or disable an adhesive component ofthe material, or any other means of reducing or eliminating the adhesiveinteraction between the materials. Some example devices for adhesionneutralizer 145 are as follows: If the neutralizing action involvescoating with or otherwise depositing or applying a material or agent,then adhesion neutralizer 145 may be a conventional printing device, anink-jet head or other aimed spraying device, a robotically guidedextrusion or tape-laying device, or any other device capable ofdepositing or applying the material or agent selectively in theproblematic region. If the neutralizing action involves irradiation,then adhesion neutralizer 145 may be a laser beam, or an LED array, or alamp shining through a mask, or another means of selectively applyingthe proper kind of radiation. After the material 146 has been treated inthis way, substrate weeding may be used because the problem materialswill no longer adhere. Negative material 17 c′ remains on substrate 13,even the negative material from the interior of the walls. When negativematerial comes into contact with adhesion-neutralized surface 146, itdoes not adhere and so is removed by substrate weeding, as is shown inFIG. 5(g). Thus, the correct result shown in FIG. 5(a) can be obtainedeither by mechanical weeding, in which case FIG. 5(a) is subsequent toFIG. 5(e), or by selective adhesion neutralization, in which case FIG.5(a) is subsequent to FIG. 5(g).

Cross-boundary linking is another factor that can hamper weeding. Thisis caused by molecular interactions between the positive and negativematerial across a cut line. It is, in effect, an attempt by the materialto “heal” the cut. Cross-boundary linking is a problem because it tendsto fight against weeding by causing the positive and negative materialto hold to each other. There are three ways this problem occurs. (a) Insubstrate weeding, when the substrate is peeled off the stackcross-boundary linking can cause negative material to remain with itsadjacent positive material instead of staying on the substrate. (b)Conversely, it may cause the material of a small positive region toremain on the substrate with its surrounding negative material insteadof adhering to the stack. Or (c), in mechanical weeding, when negativematerial is peeled from the substrate, cross-boundary linking can causethe adjacent positive material to come off with it instead of staying onthe substrate. Notice, in case (a) it is negative material that ismisbehaving, while positive material is the problem in cases (b) and(c). In cases (a) and (c), the problem is material being pulledunintentionally off of the substrate, while in case (b) it is materialbeing pulled unintentionally off of the stack. Whether these problemsoccur is governed by a relationship between the (i) strength of adhesionbetween the material in the problem region and either the substrate orthe stack, and (ii) the strength of cross-boundary linking. In a regionwith a small dimension, such as a small circle or a long, thin strip,there is a relatively large perimeter per unit surface area, andtherefore cross-boundary linking tends to be a greater problem.

Substrate weeding is preferred over mechanical weeding because substrateweeding takes no additional time to perform. But substrate weeding canonly be used when one knows for certain that the positive and negativematerial will separate when the substrate is peeled away from the stack.This is the case unless one of the following conditions holds:

There is a negative region with a small dimension such thatcross-boundary linking will hold it to the adjacent positive material,thereby pulling it unintentionally off of the substrate. In this case,it is better to use mechanical weeding (FIG. 7, and explained below), sothat the negative material is removed from the substrate before thesubstrate is conveyed to the stacker.

There is a positive region with a small dimension such thatcross-boundary linking will hold it to the adjacent negative material,thereby holding it unintentionally on the substrate. This case ishandled by using a method of selective adhesion activation (FIG. 8, andexplained below).

The negative region of the current layer touches part of the stack(negative overlap), so that the current negative material might becomeadhered to the stack and therefore be pulled off the substrate. In thiscase, one may use either mechanical weeding (FIG. 7, and explainedbelow) or selective adhesion neutralization (FIG. 5(g), and explainedabove).

III Affixing the Layers

Each layer is conveyed on the substrate to a stacker where it is broughtinto contact, in correct position, with and affixed to a stack ofpreviously-affixed layers (except for the first layer, which is affixedto a base in the stacker) to form the three-dimensional object.

Method of bonding the layers. The bonding of a new layer to the stackmay be by any of several mechanisms, such as:

(1) The inherent cohesiveness of the fabrication material.

(2) An adhesive component of the fabrication material.

(3) A physical process, such as heat-induced diffusion or melting of thefabrication material at the interface between the new layer and thestack.

(4) A chemical process, such as curing of the fabrication material or acomponent thereof.

(5) A “cold welding” process, such as self-propagating high-temperaturesynthesis (SHS), combustion synthesis, self-propagating solid stateprecursor reactions, or solid state metathesis, as described in RapidSolid-State Precursor Synthesis of Materials by John B. Wiley andRichard B. Kaner in Frontiers of Materials Science, Feb. 28, 1992, pages1093..7, or in Fundamentals of the SHS Joining Process by Robert W.Messier, Jr. and Timothy T. Orling in Materials Research SocietySymposium Proceedings, v. 314, 1993, pages 177.82. Such processes may beapplicable to fabrication of metals, ceramics, and exotic composites.

(6) Magnetism, if the fabrication material is a magnetic material, suchas Koroseal® flexible magnetic sheeting from RJF InternationalCorporation of Cincinnati, Ohio.

(7) Or any other means or process that causes the layers to bond to eachother.

The method of bonding may also involve pressing, rolling, and/or otherancillary operations to enhance the bonding achieved.

Releasable bonding. Typically, the bonding will be permanent, but it isnot necessarily so. It is also useful to use a bonding method that iscapable of being released and reactivated. After fabrication of thedesired object, the object may then be separated into sections. Thesesections may then be inspected for educational or demonstration purposesand then reassembled to reform the complete object. An example of a typeof bonding that allows this sort of behavior is cohesion of a highlyplasticised vinyl, such as is used in the manufacture of Stik-ees®glueless plastic decals by Stik-ees of Vista, Calif. Such cohesion isstrong enough to hold together a complete object, but is capable ofbeing released by moderate force along the interface between the layers,and is capable of being reactivated simply by bringing the separatedsections back into contact, as long as the surfaces have remained cleanduring their separation. Another example of a material that would allowseparation and reassembly at a cross section is magnetic sheeting, suchas Koroseal®, mentioned above.

Removal of substrate. After bonding, the substrate is removed from thenew layer in preparation for the bonding of the next following layer.The characteristics of the materials and bonding processes must be suchthat removal of the substrate does not strain the inter-layer bonding tofailure.

Use of negative material as support. In a hybrid process, when an objecthas a gently sloping, narrow, wall, which might tend to collapse in thefabrication process, that wall can be supported by negative materialadjacent to it, simply by leaving the negative material in place duringfabrication, instead of removing it. Since the wall is only slopinggently, there will not be a great deal of contact between each layer ofthe stack and the negative material of adjacent layers, so the supportstructure will fall away easily after the fabrication is complete. Acantilever can be supported by negative material in a similar way, but,since there will be a great deal of contact between the negativematerial and the first layer of the cantilever, the top layer of thesupport structure should be treated by selective adhesion neutralizationor formed from a nonadhesive material, such as ordinary paper of thesame thickness as the fabrication material. This nonadhesive materialcan be treated exactly as a sublayer, as discussed above under Methodsof varying material composition. In an additive process, material can beadded in selected negative regions to provide the same manner of supportjust described for a hybrid process.

Insertion of foreign object. The fabrication process may be interruptedat any point to insert a mechanism, electronic circuit, or other foreignobject into a void in the partially fabricated object. The fabricationprocess is then resumed.

Holding the first layer. The first layer of the desired object is formedon the substrate in the same fashion as every other layer. However,there is no stack for it to align with and bond to. Thus, thefabrication process must provide a base for the first layer to be heldto. This holding must be strong enough to support the entire desiredobject through the fabrication process, yet it must also be capable ofbeing released when the fabrication process is complete (unless it willbe desired to leave the object affixed to the base). The method ofholding may be by an adhesive that is less strong than any adhesive usedbetween the layers, or by vacuum, or by magnetism, or by any other meansor process capable of holding the first layer strongly enough, yetcapable of being released. If a hybrid fabrication process is being usedwith substrate weeding, then the base should have voids in it to matchthe negative region of the first layer. This can be accomplished bycutting the base material with the same pattern as the first layer offabrication material.

Providing for curvature of the first layer. The surface provided for thefirst layer to be held to must have the correct curvature to match thecurvature of the first layer. If the first layer is not flat, thenspecial effort is required to provide a base object with such a surface.However, this is not a difficult problem because the same fabricationequipment that will be used to build the object can first be used tobuild the base object with the proper curvature as its outermostsurface. This base object can be fabricated with holes to convey vacuumpressure, or it can be coated with an appropriate adhesive, or it can besubjected to some other process to prepare it to hold the first layer ofthe new object to be fabricated. Another way to provide for thecurvature of the first layer would be to use one of the techniqueslisted above for providing curvature of the substrate, such as acrepe-paper-like material manipulated by robotically controlled fingers,or a stretchable plastic manipulated by electromagnetically controlledrods.

Apparatus Detailed Description of an Example Carried-Sheet Fabricator

A fabrication medium 34, including a substrate 13 and a fabricationmaterial 11, which may consist of sublayers 11 a and 11 b, wheresublayer 11 b may be an adhesive, may be used with the fabrication unit100 shown in FIG. 6A. A roll of adhesive-backed vinyl or other film onpaper or other substrate is suitable. As depicted in FIG. 6A, threerolls 32 of fabrication medium 34 may be used. The fabrication medium 34from one of the three rolls 32 is selectively fed by selector rollers 36into material selector funnel 38, and then by feed rollers 39 to acutter assembly 40 where an outline of a layer is cut into thefabrication material 11 without cutting through the substrate 13. Thiscutting process is similar to that performed by a sign-cutting plotter,such as the CAMM-1 professional sign cutter from Roland Digital Group ofIrvine, Calif., or the Signmaker® automated lettering system from GerberScientific Products of Manchester, Conn. After the outline of a layer iscut in the fabrication material, the fabrication medium is sliced toyield segment 34 a containing the fabrication material of that layer(FIG. 6C).

As best shown in FIG. 6B(a), the cutter assembly 40 has base 42 whichsupports the fabrication medium 34. The fabrication medium 34 is fedbetween a contouring base 44 and a knife blade 45 which cuts the outlineof the layer but does not cut into the substrate 13. The feed rollers 39next advance the fabrication medium 34 between a slicing base 46 andslicing knife blade 47 which slices the medium into segments. Eachsegment carries a cut outline of a layer corresponding to a datapackage, including a positive region and a negative region. In certainsituations, a weeder 50 (FIG. 7) engages negative material and strips itfrom the substrate prior to the segment 34 a being advanced to thestacker 60.

After the cutting and weeding operations, the fabrication unit 100advances the segment 34 a to the stacker 60. As depicted in FIG. 6B(b),the stacker 60 comprises a U-shaped frame 72 with a roller assembly 80,including a pair of rollers 84 and 86 attached to a bracket 82 thatmoves within the frame 72 across a platform 62 which supports thestacked layers 66 of fabrication material 11. Four posts 68 at thecorners of the platform 62 support the frame 72. The axles 84 a and 86a, respectively, of the rollers 84 and 86, move along a slotted track 72a (FIG. 6C(a)) in the opposed arms of the frame 72.

The segment 34 a is advanced by a series of edge-holding rollers 74 toalign it in correct position with respect to the stack 66 of fabricationmaterial. The opposed lateral edges of the fabrication medium 34 movealong opposed channels 76 in the arms 73 a and 73 b of the frame 72. Theedge-holding rollers 74 grasp the lateral edges, feeding the fabricationmedium along the channels 76 until the segment 34 a is aligned correctlywith the stack 66.

The take-up roller 86 has a clamp 89 which grasps the forward end of thesegment 34 a as the roller assembly 80 moves to the left as viewed inFIG. 6C. As the roller assembly 80 moves to the left, the lay-downroller 84 presses the fabrication medium against the stack 66 so thatthe positive material 15 on it bonds to the stack. Substrate-weedednegative material 17 c′ remains on the substrate 13. The substrate 13,together with any substrate-weeded negative material 17 c′, becomeswaste sheet 34 b, which has its forward edge grasped by the clamp 89 andwound about the take-up roller 86 as depicted in FIG. 6C(c). When theroller assembly 80 has moved all the way to the left as viewed in FIG.6C(d), all of the waste sheet 34 b has been taken up on the take-uproller 86. The roller assembly 80 is then moved again to the right,where waste sheet 34 b is removed and discarded. The stacker 60 is thenready to receive the next segment of fabrication medium 34.

Weeder

FIGS. 7A(a)-(c) shows one example of a mechanism for weeder 50. Weeder50 mechanically removes (“weeds”) negative material 17 from substrate 13before fabrication medium 34 is conveyed to stacker 60. Fabricationmedium 34 is seen in cross section, being conveyed from the formationstation to the stacker. Boundary cuts 17 a have been cut intofabrication material 11 at the formation station, dividing fabricationmaterial 11 into positive material 15 and negative material 17. Acontinuous supply of a pickup-up film 58 is provided, on which thesurface facing fabrication material 11 is capable of being adhered tofabrication material 11. Adhesion activator 56 is provided which iscapable of activating this adhesion such that the adhesion does not takeplace except where adhesion activator 56 is engaged. As fabricationmedium 34 advances toward the stacker, adhesion activator 56 is engagedwhen a new region of negative material 17 passes under adhesionactivator 56, causing pick-up film 58 to adhere to negative material 17.Pick-up film 58 is then caused to move in unison with fabrication medium34, and negative material 17 c′ is thereby lifted off of substrate 13,leaving void 17 d.

In FIG. 7A, adhesion activator 56 is illustrated as a plunger, pick-upfilm 58 is shown to be held a small distance away from fabricationmaterial 11, as shown in FIG. 7A(a), and engagement of adhesionactivator 56 consists of moving the plunger toward fabrication material11, as shown in FIG. 7A(b). In this case, the method of adhesion ofpick-up film 58 to fabrication material 11 is by a pressure sensitiveadhesive coated on the surface of pick-up film 58 facing fabricationmaterial 11, and the adhesion is activated by pressure provided when theplunger moves toward fabrication material 11, which presses pick-up film58 against fabrication material 11. The plunger may be activated by asolenoid, by a piezo-electric element, by a mechanical cam, or by anyother mechanism capable of moving the plunger toward the fabricationmaterial. Other methods of adhesion may be used. For example, pick-upfilm 58 may be coated with a thermally activated adhesive, and adhesionactivator 56 may be a heating device, such as is used in the print headof a thermal transfer printer. After a piece of negative material 17 hasbeen adhered to pick-up film 58, fabrication medium 34 and pick-up film58 are moved in unison, as shown in FIG. 7A(c), to allow negativematerial 17 to be peeled off of substrate 13 and collected on pick-upfilm 58. Negative material 17 thereby becomes successfully weedednegative material 17 c′, leaving void 17 d in fabrication medium 34.

Adhesion activator 56 may be a single-point device which scansfabrication material 11, being engaged while passing over a negativeregion and not engaged while passing over a positive region, therebycausing negative material to be adhered to the pick-up film whileleaving positive material unaffected. Or adhesion activator 56 mayconsist of an array of single-point devices which span the entire widthof fabrication material 11 and are selectively engaged based on whichsingle-point devices have negative material under them at any one time.Alternatively, adhesion activator 56 may consist of a partial array ofsingle-point devices which span only part of fabrication material 11 andscan fabrication material 11 in order to provide adhesion to the pick-upfilm wherever required. The single-point devices in the partial arraymay be tightly spaced, so that scanning activates adhesion in successivedisjoint regions, or the single-point devices may be loosely spaced, sothat scanning activates adhesion in overlapping regions. When the methodof adhesion is by a pressure sensitive adhesive, a tightly-spacedpartial array of plungers could be similar to a print head used in adot-matrix printer.

Still another design for adhesion activator 56 calls for a separatedevice, not shown, which selectively treats fabrication material 11 tomake it susceptible to pick-up film 58 (such as by selectivelydepositing an adhesive material or agent). In this case, pick-up film 58does not adhere to raw fabrication material 11, but it does adhere tothe treated portion of fabrication material 11. (For example, if thetreatment device deposits a pressure sensitive adhesive on selectedregions of fabrication material 11, then pick-up film 58 might be aplastic or paper sheet that is attracted to this adhesive.) In thisdesign, adhesion activator 56 does not need to be selective in itsaction, but may exert its influence across the entire surface offabrication material 11; what determines which portions of fabricationmaterial 11 become adhered to pick-up film 58 is the selection ofregions that have been treated by the treatment device. As pick-up film58 passes over fabrication material 11, it picks up those regions offabrication material 11 which have been treated, and it has no effect onregions which have not been treated. However, the treatment need not beapplied to every point of a contiguous region to be weeded; it may besufficient to treat just enough of the region to allow the pick-up filmto get a hold of the region so that the rest of the contiguous regionwill follow by its innate attachment to the treated region.

FIG. 7B shows an alternative mechanism for weeder 50, which may be usedfor weeding small regions. This mechanism includes a movable weedingtool 152 on which is mounted sharp needle or barb 154, together withweed collector 250, as shown in FIG. 7B(a). Barb 154 has a bent shape ora hook shape to allow it to catch a small piece of material by beingplunged into the material (FIG. 7B(b)). Weeding tool 152 is then raisedwith small piece 17 c′ of material caught on barb 154 (FIG. 7B(c)) andweeding tool 152 is moved to weed collector 250 (FIG. 7B(d)) which hasremoval device 252 and sink 254. Removal device 252 applies a force toremove the caught piece 17 c′ of material from barb 154 on weeding tool152, as shown in FIG. 7B(e). A top view of an example weed collector 250is shown in FIG. 7B(f). Sink 254 catches the removed piece 17 c′ ofmaterial for disposal. Removal device 252 is shown to work by having ashape that allows it to surround barb 154 and push down on the caughtpiece 17 c′ of material. But other types of removal devices would workas well. For example, an alternate design of removal device may suckpiece 17 c′ of material off of barb 154 by vacuum, or blow it off by astream of air pressure, or shake it off by vibration, or pull it off byadhesion, or dissolve it away by chemical action, or any other suitablemeans.

Selective Adhesion Activation

A feature with a small dimension, such as a small circle or a long,narrow strip, can cause a problem due to cross-boundary linking. Asdiscussed under Weeding, cross-boundary linking can cause such a featureto cling to its adjacent negative material. When using substrateweeding, this may tend to lift the feature off the stack again after ithas been laid down. To prevent this problem, one can use a device toselectively activate adhesion of the particular feature to the stack.

The method of activating adhesion depends on the mechanism of adhesionat work in the fabrication materials being used. For example, if onecomponent of the fabrication material is a pressure-sensitive adhesive,then adhesion is activated by pushing the material of the featureagainst the stack. If the fabrication material is adhered by aheat-sensitive adhesive, then adhesion is activated by applying heat tothe feature.

FIG. 8 shows the use of selective adhesion activation. Adhesionactivator 182 may be one of an array of elements mounted in the lay-downplaten, or it may be an individual element or an array of elementsmounted on a mechanism that is capable of moving it to any part of thetop surface of stack 66. Alternatively, adhesion activator 182 may be aremotely scanned device, such as a laser beam, that transmits its effectto selected points on the top layer of stack 66. Adhesion activator 182may be a plunger that applies a mechanical force if the fabricationmaterial is adhered by a pressure-sensitive adhesive. Alternatively theactivator may be a heating element if the fabrication material isadhered by a heat-sensitive adhesive. Or the activator may be anotherdevice appropriate to triggering the adhesion of the material.

Selective Adhesion Neutralization on Exposed Surfaces

Selective adhesion neutralization is described above as a technique thatallows substrate weeding to be used in cases of negative overlap. Thereis another situation when it is also useful to use selective adhesionneutralization. When an object has been built in a Conveyed-Adherentfabricator, an exposed surface may be sticky because of tackinessutilized on surfaces in some implementations of the process. It would bedesirable to reduce or eliminate the tackiness on those portions of eachlayer which will be exposed in the final object. The techniquesdisclosed above for selectively neutralizing the adhesion of surfaces ina Carried-Sheet fabricator would apply equally well to this application.

FIG. 9 shows coffee cup 10 after it has been built in aConveyed-Adherent fabricator using tacky surfaces, and before beingremoved from stacker base 64. In FIG. 9(a) up-facing surface 162 ofwalls 10 a is still tacky, as is every up-facing surface during thebuild process. In FIG. 9(b), the adhesion of the up-facing surface ofthe walls has been neutralized so this surface 164 will not be stickywhen the object is removed from the fabricator to be used. In thisobject, the top half of the handle also has regions at the outer edge ofeach layer and on the very top layer that also have exposed adhesivesurfaces, but these regions are too small to be exhibited separately inthis figure.

Stacking Theory

A stacker includes a system of one or more platens, which are devicesthat impart forces on the fabrication medium to enact lay-down and/orpeel-off. The stacker also includes a system of one or more holdingdevices, which control the motion and tension of the fabrication mediumduring lay-down and peel-off. The holding system may include (a) adevice that feeds fabrication medium to the stacker, (b) a device thattakes up waste material from the stacker, (c) a system of one or morerollers that allows the fabrication medium to pass over them undertension from feed and/or take-up devices elsewhere, (d) a system ofclamping or other holding mechanisms that holds one or more of the ends,edges, or other positions of the fabrication medium in order to controlit, (e) a system of vacuum suction holes or cups, (f) or any otherappropriate means to control the motion and tension of the fabricationmedium, including combinations of the elements listed here orcombinations of these elements with other means. If any portion of theholding system holds the fabrication medium rigidly to a platen, thenthe combination of that portion of the holding system and that platen iscalled a holding platen.

An example stacker is shown in FIG. 6B(b), with additional detail of itsplaten system shown in FIG. 6B(c). In this stacker, platen system 80includes two platens: lay-down roller 84, and peel-off bar 88. Theholding system consists of edge-holding rollers 74, which holdfabrication medium 34 in position for lay-down, and take-up roller 86,which pulls up waste sheet 34 b against peel-off bar 88.

The simplest type of platen is a cylindrical platen, or roller. For anyaction of lay-down or peel-off performed by any kind of complicatedplaten system, it is sometimes useful to think of the particular localaction being performed at the point of contact of the fabrication mediumwith the stack as if that local action were being performed by a simpleroller. The radius of action is then defined as the radius of a rollerthat would provide approximately the same configuration of forces as areactually being applied.

The radius of action has several effects on the performance of lay-downand peel-off, including:

(1) The radius of action may affect how the forces of the platen aredistributed between forces tangent to the stack surface and forcesperpendicular to the surface. This may in turn affect the imposition ofdistorting stresses on the material of the stack, including the materialof the current layer.

(2) For fabricating in curved layers, the radius of action must besmaller than the radius of curvature of the layers in order to allow theaction to follow the curvature of the stack.

(3) To avoid trapping of air bubbles, the radius of action should besubstantially less than the radius of curvature of the stack.

(4) To achieve incremental pulling in peel-off, so that the platen isnot distributing its forces over a broad area, the radius of action mustbe smaller than the radius of curvature of the stack.

(5) If a holding platen is designed to hold the fabrication medium sothat the pattern for an entire layer is mounted and exposed at one time,then the average radius of curvature of the platen must be at leastequal to the length of the entire pattern divided by 6.28 (2 times pi).

Variations in stacking action. There are many variations in how thestacking (lay-down and peel-off) action may be performed. The followingfour examples illustrate choices in several aspects of the design of thesystem:

(1) Each platen may be a holding platen or a non-holding platen.

(2) A single platen may be used to perform both lay-down and peel-off,or multiple platens may be used. Multiple platens may be all similar (asin a system of rollers) or they may be dissimilar (as in a system whichuses an arc platen for lay-down and a bar platen for peel-off).

(3) Peel-off for each layer may take place after lay-down for that layeris completed (consequent peel-off), or peel-off may begin while lay-downis in progress (concurrent peel-off). In the latter case, peel-off ateach point on the stack may be approximately simultaneous with lay-downat that point (simultaneous peel-off), or peel-off at each point may beperformed with some delay after lay-down at that point (delayedpeel-off).

Consequent Peel-Off with One Holding Platen

FIG. 10A shows a method of stacking in which holding platen 85 firstpresses fabrication material 34 onto stack 66, then platen 85 reversesdirection to come back and pick up waste sheet 34 b. Platen 85 is shownas a segment of a cylinder (arc platen), but other shapes may be used,as discussed under Design of platens. The holding system is shown as apair of clamps 89, but other means may be used, as discussed underDesign of holding system for a holding platen.

FIG. 10A(a) shows fabrication medium 34 being fed into the stacker. InFIG. 10A(b), fabrication medium 34 is held to platen 85 in the properposition by clamps 89. FIG. 10A(c) shows platen 85 moved towards stack66 so that one edge of fabrication medium 34 comes into contact withstack 66. The next step is to release the one clamp 89 at the edge offabrication medium 34 which is in contact with stack 66, as shown inFIG. 10A(d). In this way, fabrication medium 34 is free to fall offplaten 85 as contact of fabrication medium 34 is extended across stack66, as is shown in FIG. 10A(e). In FIG. 10A(f), fabrication medium 34has been completely laid down, and substrate 13 is still in place on theback of the new layer of fabrication material 11, along with anynegative material 17 b which is intended to be removed by substrateweeding. Positive material 15 has become adhered to stack 66. Whenplaten 85 moves back in the opposite direction, as shown in FIG. 10A(g),positive material 15 and substrate 13 separate, positive material 15remaining adhered to stack 66 to become new layer 262, while substrate13 and any negative material 17 c′ remain held to platen 85 and togetherbecome waste sheet 34 b. When all of substrate 13 has been peeled off ofstack 66, the one clamp 89 which was released is reengaged, as shown inFIG. 10A(h), and platen 85 is moved away from stack 66, as shown in FIG.10A(i). Then FIG. 10A(j) shows waste sheet 34 b removed from platen 85for disposal.

Simultaneous Peel-Off with One Holding Platen

FIG. 10B shows a method of stacking in which holding platen 85 pressesfabrication material 11 onto stack 66 and simultaneously picks upsubstrate 13 as it progresses. Platen 85 is shown as a segment of acylinder (arc platen), but other shapes may be used, as discussed underDesign of platens. The holding system is shown as a pair of clamps 89,but other means may be used, as discussed under Design of holding systemfor a holding platen.

FIG. 10B(a) shows fabrication medium 34 being fed into stacker 60. InFIG. 10B(b), fabrication medium 34 is held to platen 85 in the properposition. FIG. 10B(c) shows platen 85 moved towards stack 66 so that oneedge of fabrication medium 34 comes into contact with the stack. Clamps89 remain engaged everywhere as platen 85 is moved so as to extendcontact of fabrication medium 34 across stack 66, as is shown in FIG.10B(d). Therefore, as positive material 15 comes into contact with stack66, it is pulled off substrate 13 onto stack 66 to become new layer 262,while substrate 13 and any negative material 17 c′ remain in place onthe platen and together become waste sheet 34 b. In FIG. 10B(e),fabrication material 11 has been completely laid down and adhered tostack 66, while waste sheet 34 b is in place on platen 85. Platen 85 isthen moved away from stack 66, as shown in FIG. 10B(f). Then FIG. 10B(g)shows waste sheet 34 b removed from platen 85 for disposal.

Simultaneous Peel-Off with One Roller

FIG. 10E shows a method of stacking in which roller 84 pressesfabrication material 11 onto stack 66 and simultaneously picks upsubstrate 13 as it progresses. In this method, roller 84 has only oneclamp 89, which grips the leading edge of segment 34 a of fabricationmedium. The trailing edge of segment 34 a is not gripped. Fender 782,which is mounted to the roller system by bracket 784, constrains segment34 a from flopping off of roller 84.

FIG. 10E(a) shows segment 34 a of fabrication medium being fed intostacker 60. In FIG. 10E(b), segment 34 a is held to roller 84 by clamp89 while roller 84 advances towards stack 66. FIG. 10E(c) shows roller84 beginning to apply new layer of fabrication material 11 to stack 66,while FIG. 10E(d) shows this new layer almost completely laid down. Aspositive material 15 comes into contact with stack 66, it is pulled offsubstrate 13 onto stack 66 to become new layer 262, while substrate 13and any negative material 17 c′ remain in place on the roller andtogether become waste sheet 34 b.

In FIG. 10E(d), trailing edge of segment 34 a is supported by fender 782to prevent it from flopping down onto stack 66 before roller 84 pressessegment 34 a into place against stack 66. In FIG. 10E(e), fabricationmaterial 11 has been completely laid down and adhered to stack 66, whilewaste sheet 34 b is dangling from roller 84. Next, clamp 89 will bereleased, allowing waste sheet 34 b to drop into a waste receptacle (notshown).

Consequent Peel-Off with a Two-Platen System

FIG. 10C shows a method of stacking in which lay-down roller 84 firstpresses fabrication medium 34 onto stack 66, then peel-off roller 88 bpulls up waste sheet 34 b. The platens are shown as rollers, but othershapes may be used. The holding system consists of a pair of movableholding rollers 172 over which fabrication medium 34 passes and isconnected to feed and take-up devices (not shown), but other means maybe used. The platen system in FIG. 10C is similar to platen system 80 inFIG. 6B(c), except that the peel-off platen in FIG. 6B(c) is a barplaten (peel-off bar 88) instead of a roller.

In FIG. 10C(a), lay-down platen 84 is pressing down against the topsurface of fabrication medium 34 in order to establish contact betweenfabrication material 11 and stack 66, while peel-off platen 88 b isidle. The left-most holding roller 172 has been placed in a positionbelow and to the left of the top of the left side of stack 66 in orderto maintain tension in fabrication medium 34 on the left side of stack66. The right-most holding roller 172 has been placed in a positionabove the right side of stack 66 in order to maintain tension infabrication medium 34 to the right of lay-down platen 84.

FIG. 10C(b) shows another view of a similar arrangement. (In FIG.10C(b), peel-off platen 88 b is not shown for simplicity, lay-downplaten 84 is shown in a raised position, and fabrication medium 34 isshown as fed over the left-most holding roller 172 instead of under itas in FIG. 10C(a).) In FIG. 10C(c), fabrication medium 34 has beenentirely laid down. Both platens 84 and 88 b are idle, and both holdingrollers 172 are maintaining tension in fabrication medium 34 on eitherside of stack 66. In FIG. 10C(d), peel-off platen 88 d is pressing upagainst the bottom surface of fabrication medium 34 in order to peelsubstrate 13 away from positive material 15 which has become adhered tostack 66 and become new layer 262. Any non-overlapping negative material17 c′ on substrate 13 is separated from positive material 15 bysubstrate weeding. Removed negative material 17 c′ and substrate 13together become waste sheet 34 b.

Delayed Peel-Off with a Multi-Platen System

FIG. 10D shows a method of stacking in which upper lay-down platen 84 cpresses fabrication medium 34 onto stack 66 against resistance of lowerlay-down platen 84 d, while lower peel-off platen 88 d pulls upsubstrate 13 from fabrication material 11 just laid down againstresistance of upper peel-off platen 88 c. The platens are shown asrollers, but other shapes may be used. The holding system includes apair of stationary holding rollers 172 over which fabrication medium 34passes and is connected to feed and take-up devices (not shown), butother means may be used.

Design of Platens

The terminology used here is as follows. The “face” of a platen is thatportion of the surface of the platen which contacts a fabricationmedium. The “shape” of a platen refers to the shape of the platen'sface. A smooth surface may either be flat (have no curvature), singlycurved (have single curvature), or doubly curved (have doublecurvature). This refers to the number of straight lines that can bedrawn in a smooth surface through a point in the surface. If twodifferent straight lines can be drawn through a point, then any linethrough the point is straight, and the surface is flat at that point. Ifonly one straight line can be drawn through a point, then the surface issingly curved at that point, and the straight line is the axis ofcurvature at that point. If no straight lines can be drawn through apoint, then the surface is doubly curved at that point.

A platen may have any of a variety of shapes. These are discussed herein three broad categories: constant single curvature, flexiblecurvature, and controlled curvature. A flat platen is not generallyuseful because (a) in lay-down, it may be prone to trapping air bubblesbetween the new fabrication material and the stack, and (b) in peel-off,it does not provide for a means to incrementally separate the substratefrom the fabrication material. However, a flat platen may be used if ithas controlled curvature, as discussed below. For fabrication in doublycurved layers, it may be necessary to use a fabrication medium that iscapable of conforming to a doubly curved shape. In the jargon of thecomposites industry, this ability in a material is called “drape.”

Platen with constant single curvature. A platen with single curvature isuseful for fabricating objects in flat layers or in layers of singlecurvature. Examples of singly-curved platens include a cylindricalplaten, or roller, as shown in FIG. 11A(a), an arc platen, which is asection of a cylinder and has a constant radius of curvature, as shownin FIG. 11A(b), a more general singly-curved shape, as shown in FIG.11A(c), a bar platen, as shown in FIG. 11A(d), and a blade platen, whoseface is just a pointed edge, as shown in FIG. 11A(e).

To allow for fabrication in singly curved layers, a cylindrical platenor roller (with radius smaller than the radius of curvature of thelayers) may be mounted on a mechanism that allows it to be raised andlowered as it passes over the stack. This is shown in FIG. 11A(f), whereaxle 84 a of roller 84 is driven up and down in tracks 72 b while beingdriven back and forth in tracks 72 a. If the axes of curvature at everypoint of stack 66 are horizontal, then platen 84 may remain horizontalas it is raised and lowered, so that both sides of platen 84 may beraised and lowered in unison. If, however, the axes of curvature are noteverywhere horizontal, then each side of platen 84 must be capable ofbeing raised and lowered independently to allow platen 84 to follow thecurvature of stack 66.

FIG. 11B shows the use of a peel-off bar, which is a bar platen used forthe same purpose as upper peel-off platen 88 c in FIG. 10D. In FIG. 11B,there is no lower peel-off platen, and waste sheet 34 b is fed directlyfrom peel-off bar 88 to the holding device, which for purposes ofillustration only in this figure is shown as take-up spool 86. Thesequence of actions in FIG. 11B is such as would be carried out afterfabrication medium 34 has been laid down by a separate lay-down platensystem (not shown). In FIG. 11B(a), peel-off bar 88 is positioned over anegative region, so negative material 17 under peel-off bar 88 remainson substrate 13, In FIG. 11B(b), peel-off bar 88 has reached boundarycut 17 a in fabrication material 11. Negative material 17 separates frompositive material 15, becoming successfully weeded negative material 17c′ and together with substrate 13 becoming waste sheet 34b, whilepositive material 15 remains adhered to stack 66 and becomes new layer262. In FIG. 11B(c), substrate 13 is being peeled away from positivematerial 15 on stack 66. In FIG. 11B(d), peel-off bar 88 has reachedanother boundary cut 17 a. Again the negative and positive materialseparate, with negative material 17 remaining on substrate 13.

The advantage of a bar platen is that it provides a very small radius ofaction, which can be helpful for certain types of fabrication material.An even smaller radius of action is obtained by using a blade platen(FIG. 11A(e)).

Platen with flexible curvature. For fabrication in doubly curved layers,a platen with flexible curvature is useful because the platen mayconform passively to the curvature of the stack. Two examples arediscussed here: a pillow platen and a sausage platen. A pillow platenmay be useful for fabrication in layers with mild, double curvature. Asausage platen may be able to operate on stacks of more gross curvature.

A pillow platen is a holding platen with flexible double curvature. Itis like a pillow because (a) left alone, it's face has a gentle doublecurvature with simple symmetry, but (b) it's face is capable of takingon any sort of complicated curvature in response to forces applied tothe face. This allows such a platen to be used to apply fabricationmaterial to layers of complicated curvature because as the platenpresses the material against the stack, the face of the platen and thematerial mounted on it can conform to the shape of the stack, allowingeach part of the fabrication material to contact the correct point ofthe stack. Since the platen conforms to the shape of the stack instages, it allows air to be pushed out of the way in the process insteadof becoming trapped between the fabrication material and the stack.After the fabrication material has conformed to the shape of the stackand become adhered to it, the platen is pulled away from the stack. Asthe platen is pulled away, the substrate separates from the fabricationmaterial. The portions of the fabrication material which were the lastto come into contact with the stack are the first to be separated fromthe substrate.

The flexibility of a pillow platen may arise from being made of aflexible material, such as rubber, foam, or sponge, or the face of theplaten may be a thin, stretchable material filled with such a flexiblematerial or filled with a fluid, such as water, oil, or air. If theplaten is filled with a fluid, one could adjust its flexibility bycontrolling the fluid pressure of the fluid.

The use of a pillow platen is illustrated in FIG. 11C. FIG. 11-C(a)shows fabrication medium 34 being fed to platen 480. In FIG. 11C(b)fabrication medium 34 is mounted to the face of platen 480 and held tothe face by a holding means, which for the purposes of illustration onlyis shown here as a set of clamps 89. Opposite the face of platen 480 isshown stacker base 64, whose shape is used to establish the shape of thefirst layer of the object to be built. When platen 480 is moved towardsbase 64 and fabrication medium 34 contacts base 64, the face of platen480 and fabrication medium 34 together conform to the shape of base 64and fabrication material 11 becomes adhered to the base 64. (Thisadhesion is releasable, as is discussed under Holding the first layer.)Then platen 480 is moved in the opposite direction to pull it away frombase 64, whereupon substrate 13 is incrementally separated fromfabrication material 11. FIG. 11C(c) shows a result of severalrepetitions of this procedure. In FIG. 11C(c), the curvature of thelayers is seen to vary from layer to layer. Methods for accomplishingthis are discussed under Methods of Varying Curvature of Layers. If thelayers are formed on the substrate either in a flat configuration orwith a curvature which is different from the final curvature which theywill assume on the stack, then the thickness of the layers as formed canbe adjusted for the changes that will take place in the curvature asdiscussed under Accommodating thickness of layers to changes incurvature.

A sausage platen consists of chain of roller segments 682 joinedtogether by linkages 684, as shown in FIG. 11D(a). A sausage platen canroll over a surface of complex curvature, pressing down uniformly on amajor portion of the surface area. The downward force of a rollersegment may be provided by its weight, by a set of push-rods 688 (asshown in FIG. 11D(b)) connected to the roller segment by yokes 686, orby another appropriate means.

Platen with controlled curvature. A platen may be provided with means tovary the curvature of its face under computer control. This allowsforces to be selectively applied to portions of a fabrication mediummounted on it. The forces applied may be either to push the fabricationmedium against the stack during lay-down, or to pull the substrate awayfrom the stack for peel-off. The idea is to use controlled changes inthe curvature of the platen face either (a) to push on the fabricationmedium in different parts separately in order to selectively “roll” onthe fabrication material, and/or (b) to pull on the substrate indifferent parts separately in order to selectively peel off thesubstrate.

Controlling the curvature of a platen face can be implemented in aplaten of any starting shape, and consists of inducing changes in thatstarting shape. The ability to do this generally requires that (a) theplaten face be constructed of a flexible, stretchable material, and (b)there is mounted under the face material a mechanism for applying forcesto the face material to control its shape. The mechanism for applyingthe forces may consist of rollers, pins, or other elements to convey theforces. FIG. 11E shows flat platen 580 with controlled curvatureimplemented by roller 584 moving beneath its face 382. FIG. 11E(a) is across section, while FIG. 11E(b) shows platen 580 in full-face view.FIG. 11E(a) and FIG. 11E(b) show platen 580 with roller 584 in its“rest” position, where it does not affect the curvature of face 382.FIG. 11E(c) shows platen 580 in cross-section with roller 584 in aposition where it is imposing curvature on a portion of platen face 382,and is therefore pushing on the corresponding portion of fabricationmedium 34.

An application of the ability to control the curvature of a platen facearbitrarily is in building an object that has cantilevers or overhangsextending in all directions. Overhangs cause a problem for removal ofthe substrate because the substrate cannot be removed by lifting in adirection that first raises the overhanging material. For overhangs thatgo all the way around an object, this means that the substrate has to beremoved by lifting first in the interior of the object and pullingtowards the outside. This is best done with a platen whose facecurvature can be modified under computer control. (An alternativesolution to this problem is to use support structures that fill in partof the space under the overhang.)

Design of holding system for a holding platen. A fabrication medium maybe held to a platen by various means. The requirements of the holdingmeans are that (a) it holds the fabrication medium securely to theplaten without wrinkling or buckling and without allowing air to betrapped between the substrate and the platen, and (b) it is easilyreleasable. Three examples are shown in FIG. 12, although others mayalso be used. One example is the use of clamps 89 at opposite edges offabrication medium 34, as shown in cross section for arc platen 85 inFIG. 12(a), for arc platen 85 with a full-face view of the platen inFIG. 12(c), and in cross section for cylindrical platen 84 in FIG.12(h). FIG. 12(b) shows a possible mechanism for operating clamps 89.When solenoid 282 is energized, it pulls solenoid pin 282 b intosolenoid body 282 a against the force of spring 282 c, thereby pullingclamp 89 against fabrication medium 34. Another example is the use of aseries of edge-holding rollers 74 along opposite edges of fabricationmedium 34, as shown in cross section in FIG. 12(d) and with a full-faceview of the platen 85 in FIG. 12(e). Still another example is the use ofvacuum suction, as shown in cross section in FIG. 12(f) and with afull-face view of platen 85 in FIG. 12(g). In FIG. 12(f), the smallarrows indicate the force of suction acting on fabrication sheet 34 dueto an array of tiny vacuum holes along the surface of platen 85. In FIG.12(g), the array of holes is indicated by dots, which are shown in thefigure but are actually hidden beneath fabrication medium 34.

FIG. 10A and FIG. 10B also show the use of clamps 89 at opposite edgesof the fabrication medium, but this is only for purposes ofillustration. Other means, or a combination of means, may be substitutedin these figures without affecting their meaning.

When mounting fabrication medium 34 to cylindrical platen 84 (roller),it will generally be advisable to slice fabrication medium 34 intosegments 34 a. When using an arc platen 85, however, one may slicefabrication medium 34 into segments or one may hold to platen 85sections of a long, continuous sheet.

When the holding means involves clamps 89, one or more of clamps 89 maybe mounted in a track 284 which allows the clamp 89 so mounted to berepositioned for use with a shorter segment 34 a of fabrication mediumor with a shorter section of a long, continuous sheet of fabricationmedium 34. This is shown in cross-section for cylindrical platen 84 inFIG. 12(i), in cross-section for arc platen 85 in FIG. 12(j), and forarc platen 85 with a full-face view of the platen in FIG. 12(k). In FIG.12(i), FIG. 12(j), FIG. 12(k), the dotted lines represent alternativepositions of the repositionable member of the set of clamps 89.

FIG. 12(l) shows a variation on the use of clamps 89 with cylindricalplaten 84, in which there is only one clamp 89. Segment 34 a offabrication medium is wrapped completely around roller 84 and overlapson itself so that two edges may both be clamped by the single clamp 89.This technique may be used for concurrent peel-off, but not forconsequent peel-off because it does not allow holding means 89 to bereleased at one edge of segment 34 a while remaining engaged elsewhere.This technique also requires that segment 34 a be long enough tosufficiently exceed the circumference of roller 84.

FIG. 10E shows a variation in which a single clamp 89 is used to holdone edge of segment 34 a of fabrication medium, while the other end ofsegment 34 a is left free.

Brief Description of an Example Carried-Sheet Fabricator withEndless-Belt Substrate

In FIG. 13, an alternate embodiment of this invention is shown where thesubstrate 13 consists of sections of an endless conveyer belt 33. Inthis embodiment, a roll 32 of fabrication material 11 advances to engagethe surface of the belt 33 which carries the fabrication materialbetween knife blade 45 and base 44. The blade 45 cuts through thefabrication material 11 to form on the substrate 33 a positive regionand a negative region of the material. The belt then conveys thematerial 11 to stack 66 where the positive material is removed andadhered to stack 66. The endless belt 33 continues to carry the negativematerial on its surface and advances this negative material to astripper 49 which is a blade which scrapes along the surface of thesubstrate to remove the negative material. The embodiment depicted inFIG. 13 provides for continuous use of the substrate.

Brief Description of an Example Carried-Sheet Fabricator with ContinuousTake-Up of Scrap

In FIG. 14, an embodiment of this invention is shown where fabricationmaterial 34 is supplied on roll 32 of long, continuous sheet and is notsliced into segments. As each section of fabrication medium 34 istransformed into waste sheet 34 b by the removal of positive material 15therefrom and the attachment of the positive material on stack 66, saidwaste sheet 34 b is wound up on take-up spool 86. For this to work, aregion of fabrication medium slack 34 c must be created betweenformation station 40 and stacker 60 so that fabrication medium 34 mayundergo independent motions and have different tensions in formationstation 40 and in stacker 60. The proper slack 34 c is maintained byfeed rollers 39.

Brief Description of an Example Additive Conveyed-Adherent Fabricator

In FIG. 15, an alternate embodiment of this invention is depicted whichis similar to that shown in FIG. 13. The principal difference is thatthe additive version of the method is employed where material isselectively deposited on the belt 33. A suitable deposition material is,for example, a hardenable paste or gel. In accordance with thisembodiment, the material is deposited as a layer with precise,predetermined boundaries so that no negative material is present on thesubstrate. A suitable deposition device 45 a may be a drop-on-demand inkjet as used in the Hewlett-Packard DeskJet printer, or a continuous-modeink jet as used in the Soligen DSP fabricator.

One of the important features of this invention is the use of successivecarrier substrates 13 to convey fabrication layers. The same substrate,however, may be repeatedly reused and moved reciprocally between theformation station and the stacker, or the substrate may be discardedafter each use. Each is considered successive carrier substrates.

Scope of the Invention

The above presents a description of the best mode contemplated ofcarrying out the present invention, and of the manner and process ofmaking and using it, in such full, clear, concise, and exact terms as toenable any person skilled in the art to which it pertains to make anduse this invention. This invention is, however, susceptible tomodifications and alternate constructions from that discussed abovewhich are fully equivalent. Consequently, it is not the intention tolimit this invention to the particular embodiment disclosed. On thecontrary, the intention is to cover all modifications and alternateconstructions coming within the spirit and scope of the invention asgenerally expressed by the following claims, which particularly pointout and distinctly claim the subject matter of the invention:

What is claimed is:
 1. Apparatus for selectively removing sheet materialfrom a carrier substrate, including a formation station where the sheetmaterial on the carrier substrate is divided into a negative region ofwaste material and a positive region corresponding to a predeterminedconfiguration, and a weeder mechanism which selectively removes thenegative region of waste material from the carrier substrate, saidweeder mechanism including a barb element that selectively engages andretains a negative region of waste material until said retained negativeregion of waste material is removed from the barb element.
 2. Apparatusfor fabricating a three-dimensional object from individual layers offabrication material having a predetermined configuration, wheresuccessive layers are stacked in a predetermined sequence and affixedtogether to form said object, said apparatus including a formationstation where successive, individual fabrication layers are formed onsuccessive carrier substrates, said individual fabrication layers beingdivided into a negative region of waste material and a positive regioncorresponding to the configuration of one individual layer, a stackingstation where the successive, individual fabrication layers are stackedtogether to form a stack, a conveyor for conveying the successive,individual fabrication layers on said successive carrier substrates fromsaid formation station to said stacking station, a separator whichseparates each successive carrier substrate from the fabrication layerthereon to expose a bonding surface on each individual fabricationlayer, a weeder mechanism in advance of the stacking station whichselectively removes the negative region of waste material from thefabrication layers, said weeder mechanism including a roller device thatretains thereon the substrate, and any negative region adhering thereto,to expose an internal surface of the individual fabrication materialbeing deposited so that a successive fabrication layer may be bondedthereto, and an affixing mechanism which brings an individualfabrication layer into contact with the stack, so that the layer becomesaffixed to the stack.
 3. Apparatus for fabricating a three-dimensionalobject from individual layers of fabrication material where successivelayers are stacked in a predetermined sequence and affixed together toform said object, said apparatus including a continuous roll of carriersubstrate having thereon a continuous layer of fabrication material, aformation station where successive, individual fabrication layers areformed on the carrier substrate by dividing successive segments of thecontinuous layer of fabrication material into a negative region of wastematerial and a positive region corresponding to the configuration of oneindividual layer, a stacking station where the positive regions of thesuccessive segments of the continuous fabrication layer are sequentiallystacked to form the object, a conveyor for conveying -the successivesegments formed at the formation station to said stacking station on thecontinuous carrier substrate, an affixing and separating mechanism whichaffixes said positive region to a stack of layers at the stackingstation and separates the positive region of each successive segmentfrom the carrier substrate, and a weeder mechanism that selectivelyremoves any negative region of waste material from the fabricationlayers including a roller device that retains thereon the substrate, andany negative region adhering thereto, to expose an internal surface ofthe individual fabrication material being deposited so that a successivefabrication layer may be bonded thereto.
 4. The apparatus of claim 3where a portion of said continuous carrier substrate between saidformation station and said stacking station is maintained by saidconveyor in a slack state.
 5. Apparatus for fabricating athree-dimensional object, including a formation station providing asheet material including a carrier substrate and a fabrication materialformed into a predetermined configuration on the carrier substrate, astacking station at which a series of successive, individual layers offabrication material are formed into a stack, a weeder mechanism inadvance of the stacking station which selectively removes any negativeregion of waste material from the layers, said weeder mechanismincluding a roller device that retains thereon the substrate, and anynegative region adhering thereto, to expose an internal surface of theindividual fabrication material being deposited so that a successivefabrication layer may be bonded thereto, and an affixing and separatingmechanism at said stacking station which affixes the fabricationmaterial on the substrate to the stack and then separates the carriersubstrate from the individual fabrication layer affixed to the stack,said affixing and separating mechanism including a platen device aboutwhich the sheet material is wrapped, said platen device being movedalong a path adjacent the stack, bearing against the stack to depositthe fabrication material onto the stack, said platen device as it movesalong said path retaining on said platen device the substrate. 6.Apparatus for fabricating a three-dimensional object from a flexiblesheet member comprising a substrate and a fabrication material having anexterior surface and an internal surface carrying an adhesive whichbonds the fabrication material to the substrate but allows the substrateto be removed to expose the adhesive upon separation of the substratefrom the fabrication material, said apparatus including a stackingstation at which a series of successive, individual layers offabrication material are formed into a stack, a cutter in advance of thestacking station which partially severs the sheet member, cuttingthrough the fabrication material but not the substrate to form on thesubstrate a positive region corresponding to a predeterminedconfiguration for an individual layer of fabrication material and anegative region of waste material, and an affixing and separatingmechanism at said stacking station which receives the sheet materialfrom the cutter and separates each successive carrier substrate from theindividual fabrication layer thereon to expose said adhesive on saidinternal surface of the individual fabrication layer, said affixing andseparating mechanism including a roller device about which the sheetmaterial is wrapped, said roller device being moved along a pathadjacent a previously stacked fabrication layer which has its adhesivebearing, internal surface exposed, bearing against the previouslystacked fabrication layer to deposit the fabrication material carried bythe roller device on said exposed, adhesive bearing, internal surface ofsaid previously stacked fabrication layer, with the adhesive on saidinternal surface of said previously stacked fabrication layer bonding tosaid exterior surface of the individual fabrication material, saidroller device as it moves along said path retains on said roller devicethe substrate, and any negative region adhering thereto, to expose theinternal surface of the individual fabrication material being depositedso that a successive fabrication layer may be bonded thereto.
 7. Theapparatus of claim 3 where the roller device is first moved in onedirection to deposit the sheet material, including both the substrateand the individual fabrication layer thereon, on the previously stackedfabrication layer, and then moves in an opposite direction to separatethe substrate and any negative region of waste material thereon from thedeposited fabrication layer.
 8. Apparatus for fabricating athree-dimensional object from a flexible sheet member comprising asubstrate and a fabrication material having an exterior surface and aninternal surface carrying an adhesive which bonds the fabricationmaterial to the substrate but allows the substrate to be removed toexpose the adhesive upon separation of the substrate from thefabrication material, said apparatus including a stacking station atwhich a series of successive, individual layers of fabrication materialare stacked in a predetermined sequence and affixed together to form astack, a cutter in advance of the stacking station which partiallysevers the sheet member, cutting through the fabrication material butnot the substrate to form on the substrate a positive regioncorresponding to a predetermined configuration for an individual layerof fabrication material and a negative region of waste material, aconveyor for conveying in said predetermined sequence partially severedsheet members to said stacking station, and an affixing and separatingmechanism at said stacking station which separates each successivecarrier substrate from the individual fabrication layer thereon toexpose said adhesive on said internal surface of the individualfabrication layer, said affixing and separating mechanism including aroller device which is moved along a path adjacent the stack, saidroller device bearing against the sheet member so that the exteriorsurface of the fabrication material contacts said exposed adhesive,bonding to said stack, said roller device as it moves along said pathpulling the substrate, and any negative region adhering thereto, fromthe individual layer to expose its internal surface so that successivefabrication layers may be bonded thereto, said roller device being movedin a sequence so that said exterior surface of said individualfabrication layer is bonded to the stack prior to separation of thesubstrate from said individual fabrication layer.
 9. The apparatus ofclaim 8 where the roller device moves first to bond selectively theindividual fabrication material to the stack and moves again to pull thesubstrate, and any negative region adhering thereto, from saidindividual fabrication layer bonded to the stack.
 10. The apparatus ofclaim 8 where the roller device includes a set of spaced apart parallelrollers.
 11. The apparatus of claim 10 where one of the rollers includesa gripper mechanism which grips an edge of the sheet member and pullsthe substrate, and any negative region adhering thereto, from the stack.12. The apparatus of claim 8 including a waste material removingmechanism which removes, at least partially, the negative region offabrication material from the substrate prior to the affixation of thelayers.
 13. Apparatus for fabricating a three-dimensional object from afabrication material held to a substrate in a way that allows thesubstrate to be separated from the fabrication material when successivelayers of fabrication material are affixed together, said apparatusincluding a stacking station at which a series of successive, individuallayers of fabrication material are stacked in a predetermined sequenceand affixed together to form a stack, each of said successivefabrication layers being formed on the substrate as an individual layercomprising a positive region corresponding to a predeterminedconfiguration for an individual layer of fabrication material and anegative region of waste material, said negative region including andinterfering negative region and a non-interfering negative region, acutter which cuts through the fabrication material but not the substrateto form the positive and negative regions, a fabrication materialremoval mechanism in advance of the stacking station which selectivelyremoves substantially all of said interfering negative region from thesubstrate prior to stacking of said individual fabrication layers, aconveyor for conveying in said predetermined sequence the successive,individual fabrication layers on one or more carrier substrates to saidstacking station, an affixing mechanism which brings a bonding surfaceof the stack into contact with the fabrication layer, so that the layerbecomes affixed to the stack, and a separator which separates from thefabrication layers each successive, individual carrier substrate withany remaining non-interfering negative region remaining thereon afteraffixation of the previous individual fabrication layer to the nextsuccessive fabrication layer.
 14. The apparatus of claim 13 including agripper mechanism which grips an edge of a substrate and pulls thesubstrate, and any negative region adhering thereto, from stacked layersaffixed together.
 15. Apparatus for fabricating a three-dimensionalobject from a sheet material, said apparatus including a dividingstation at which successive segments of sheet material on a flexiblesubstrate material are divided into regions of positive materialcomprising the sheet material that is to be part of the said object andregions of negative material comprising the sheet material that is notto be part of the said object, a stacking station at which a successionof such divided segments of sheet material is stacked in a predeterminedsequence and affixed together to form said object, a conveyor that movesthe substrate material with divided segments of sheet material thereonto said stacking station, an affixing and separating mechanism at saidstacking station which (i) brings each new segment of sheet material inthe said sequence into contact with a surface of the stack of previoussegments of sheet material so that the said new segment becomes affixedto the stack, and (ii) separates the substrate material from the saidnew segment of sheet material thereon by incrementally pulling thesubstrate material from the sheet material.
 16. The apparatus of claim15, where the sheet material includes an adhesive component.
 17. Theapparatus of claim 16, where the adhesive component is substantiallymixed in with the rest of the sheet material.
 18. The apparatus of claim16, where the adhesive component is a coating on the rest of the sheetmaterial.
 19. The apparatus of claim 15, including a bond-inducingmechanism that performs an operation which causes or enhances bonding ofeach new segment of sheet material to the said surface of the stack. 20.The apparatus of claim 19, where the bond-inducing mechanism operatessubstantially uniformly on all parts of each new segment of sheetmaterial.
 21. The apparatus of claim 19, where the bond-inducingmechanism operates only on geometrically selected portions of each newsegment of sheet material.
 22. The apparatus of claim 15, where thedividing station includes a cutting mechanism that cuts through thesheet material without cutting through the substrate material.
 23. Theapparatus of claim 15, including a weeding station between the dividingand stacking stations, which weeding station removes selected portionsof negative material from the substrate material prior to the stackingof each new segment of sheet material.